McLean Gardens Residents Association chairman Jack Koczela and his wife Julie have to be two of the classiest squatters around.

Jack, 28, of a carefully-clipped beard and tweed jackets, and Julie, 27, who almost simultaneously changes her car's oil and arranges a vase of flowers, will be people to watch as the McLean Gardens' Limited Partnership progresses.

He -- who took a year off from work to fight for tenants -- is a history graduate of American University and former executive director of admissions there. She has a masters degree in urban and regional planning from George Washington University, and is now development coordinator for the Gardens.

As leaders in perhaps the largest tenant conversion in the country -- possibly the only one with a partnership in property development, functioning as both cooperative and condominium -- both are committed to retaining some of the Gardens' original ambience.

Says Jack: "We know -- and always have -- that we're sitting on some of the most fantastic property in this city, if not in the country. We've been saying all along, 'Hey, listen to the tenants who've lived here and know what they value.' There's nothing that's going to be put up on that property without our consent. We know we're in the public eye. We have to be better than anyone else."

Julie: "Two years ago, we hoped that all of the Gardens could remain moderately-priced rentals, but that didn't work out, so our hope now is that we can retain a very diverse community with a wide range of incomes and interests. cWe may be outnumbered [they own 150 units out of the projected total of about 1,350], but we're strong."

Jack: "When I look back on the early tenant association pictures, I see lots of elderly faces in the crowd. A lot of them are gone, and I'd like to see them back again."

Julie: "We're hoping that we can set aside one building for the elderly, but we'll have to work out the design so they can get in and out easily." (The cooperative part of the complicated Gardens arrangement will have its own architects and its own financial consultants.)

All of the present cooperative members are expected to receive 7 1/2 percent HUD financing, and they have applied for additional (Section 8) government subsidizing of other units. "Also," says Julie, "we could use any profits from the overall development for more lower-income housing."

There is already a waiting list of hundreds for the cooperative phase of the development. "You wouldn't believe," says Jack, "the number of people who couldn't stick it out, who now want back in."