On the whole, said Arlington developer Paul V. Cali as he strolled down the steaming pavement of Wilson Boulevard last week, he'd rather be riding one of the 50 horses on his Wyoming ranch.

But it was in Arlington's booming Ballston neighborhood, just off the I-66 interchange with Glebe Road, where Cali and two partners have cut one of the biggest real estate deals in the Washington area.

Across the street, the shell of a $100 million shopping center-office complex is going up on the site of the old Parkington shopping mall. On Cali's side of the street, the owners of a ragtag collection of decades-old retail shops are planning to close their doors, their pockets newly bulging with the proceeds of the deal Cali arranged.

The property owners -- including White House chief of staff Donald T. Regan and the county government -- are cashing in on a $200 million residential and commercial complex that, Cali and his partners disclosed last week, they will build in the heart of Ballston. They have been working on the proposal for six years, negotiating with 26 parties.

"I looked at an awful lot of contracts before I signed," Dillard Coleman, owner of Cycles Arlington, said as he recalled other developers' courtship for his 19,789-square-foot lot at 4219 Wilson Blvd.

"But the others couldn't see clear to put the right money up and assemble all the lots," he said, praising the $80-a-square-foot offer that Cali's group made.

There were times when Cali, a 43-year-old former marine who came to Washington when he was assigned to Quantico after Vietnam, had qualms about whether he could pull the deal together.

"I was beginning to have self-doubts about whether we were too premature," he said. "[But] my wife says I suffer from a dangerous amount of self-confidence. Intuitively, I knew we had a winner."

If the project, known as Stafford Place at Ballston, wins County Board approval later this year -- as some version of it is expected to -- it will be one of the most massive projects built in Arlington: almost 1.5 million square feet of building space on 5.6 acres with four 13-story office buildings and two 22-story residential buildings.

"In the late seventies, we were looking for an area we felt had growth potential but had not been discovered, so to speak, by mainline developers," Cali said. With that goal, Cali and partners C.O. North of Potomac and Robert V. Glamb of McLean began their search.

Cali said the partners are still in the preliminary stages of arranging financing on the project and expect they will have little difficulty securing the more than $200 million the project will require now that they have assembled the land.

Cali won't estimate his share of the profits from the project, his first major undertaking. More typical of his work is the $3.2 million renovation of the Arlington Forest Shopping Center at Rte. 50 and Park Drive.

"We are not Ollie Carr or Charles E. Smith," Cali said, referring to two of the most prominent developers in the area.

Although Cali, North and Glamb began buying parcels in the county's Clarendon area, near another station on the Metro line, they eventually turned west to a two-block area near the planned Ballston Metro station and bounded by Wilson Boulevard and North Randolph, North Stuart and North Ninth streets.

"The reason our attention was drawn to this project is that it had a unique location," said Cali. It had Metro, planned for 1979, and the much-touted renovation of the aging Parkington center into a new mall.

Many owners of nearby small businesses at Ballston, jaded by the collapse of many previous plans to renovate Parkington, held out.

But Cali, a founder of the Ratcliffe Cali real estate consulting firm 20 years ago, said: "I had expected three years ago to see more activity from the better-known development community around town . . . [and] the delays in starting the shopping center caused a lot of consternation for us."

Perhaps the most important factor in assembling the land, he said, was the county's "foresight and understanding [of] the economic realities" of land consolidation by creating a zoning district for central Ballston in early 1980. "That's what kicked it off; that's what made it all possible," Cali said.

The area's high-rise zoning category, known as Commercial-Office-Apartment, is unique in Arlington. It provides a complex sliding-scale formula that determines allowable heights and densities for the ground space involved.

Its chief function, says county economic development chief Thomas C. Parker, is to encourage developers to consolidate properties and thereby gain greater densities. "It's a bargaining chip to discourage holdouts," Parker said.

Another key element, Parker said, is the zoning provision's requirement that at least half the building space be residential. That caveat was created by the county to discourage the ghost-town effects after working hours in areas dominated by office buildings, a complaint often made about Rosslyn, one of Arlington's first high-rise neighborhoods. A developer who does not want to build residences effectively gives up half the allowable floor area, making the project more costly, Parker said.

Because the zoning category was developed with the participation of the Ballston community, little neighborhood opposition to the Cali project is expected. County officials said, nonetheless, they expect to be lobbied for some changes in the project.

When Cali snatched up the requisite amount of land to make the project work under the special zoning, he said, the other property owners soon agreed to sell. Today, he said, he doubts that "there is a site available [in Ballston] that isn't in the hands of a development company by now" because of the zoning.

Developer Robert E. Buchanan, the local partner for Radnor Corp., which is in the process of buying up a block near the Cali project, said that Radnor is anxiously monitoring Cali's success. Radnor, a wholly owned subsidiary of the Philadelphia-based Sun Co., is putting up a 12-story office building in Ballston at 4601 N. Fairfax Dr.

It was 18 months ago that Cali said he "knew we had clinched it." The process began in 1979, when the partners signed their first purchase contract with a plumbing warehouse, and ended last week when they wrapped up the last of 26 negotiations involving 19 parcels, ranging from 7,200 square feet to 38,600 square feet. Leaseholders also had to be bought out.

Among those who have agreed to sell are the Arlington County government, which owns 14,870 square feet at 4214 N. Ninth St., and White House chief of staff Regan and his wife Ann, who own 7,759 square feet at 4213 Wilson Blvd.

The negotiations, Cali said, dealt with "very well-heeled old-line real estate types who had owned their property for generations to the small mom-and-pop retail store owners like the Sleep Shop. From the toughest, most ruthless negotiating team to the nicest people you'll ever meet."

"He's a very fine person," said Kathryn Long, whose husband's family bought the Sleep Shop bed and mattress store at 4115 Wilson Blvd. almost 45 years ago. The Longs have negotiated with Cali for almost three years.

"We felt it would eventually happen," she said. "At first we thought we'd try to stay. But as the plans developed we realized we would just be an old building among new things." CAPTION: Picture, Paul Cali's proposed $200 million Stafford Place at Ballston would be one of the most massive projects built in Arlington.