Michigan and Texas appear to be the leading contenders for the location of General Motors' new Saturn Corp. manufacturing complex, corporate officials said today.

GM officials said announcement of the plant location should be made before the end of the month. "We are 99 percent finished with all of the computer runs and other analyses" being used in the selection process, one GM source said.

The source said that some last-minute problems could delay the site-selection announcement for several more weeks. But other GM sources said that such a delay is unlikely.

GM's top executives have not yet settled on a most-favored site, according to several company sources. But they said they would not dispute reports from other GM and U.S. auto industry officials that the Midwest and the Southwest in general, and Michigan and Texas in particular, appear to be the leading contenders.

The winner will get one of the most ballyhooed manufacturing facilities of the century -- a superautomated car manufacturing and assembly complex designed to revolutionize small-car production in America.

Saturn also would be the site of one of the most ambitious labor-management experiments in the history of U.S. manufacturing -- an amalgam of novel, flexible work rules tried in piecemeal fashion elsewhere. Chief among those changes could be the installation of a fully salaried work force in an industry geared to hourly wages for blue-collar employes.

One ranking GM official confirmed in an interview that the company and the United Auto Workers union at Saturn are giving serious consideration to putting traditional hourly employes on annual salary.

The pay plan and other aspects of the UAW's Saturn labor agreement probably will be announced when GM reveals the selected site, GM officials said.

GM began feasibility studies on a Saturn site in December 1983. By Jan. 8, 1985, when GM announced creation of Saturn Corp. as a separate but wholly owned GM company, an estimated 20 sites had been surveyed by Argonaut Realty, the auto maker's real estate development arm. But the site search was broadened -- and made more complicated -- after the Saturn Corp. announcement. "We began hearing from parts of the country we never heard from before," one GM official said.

Governors flocked to Detroit. State after state and hundreds of municipalities filed applications for the proposed complex.

Today, at Argonaut offices adjacent to GM's world headquarters here, 80 legal-size file drawers bulge with well-documented appeals from Saturn contenders.

Most of these applications were subjected to repeated computer analyses aimed at gathering "hard data," such as tax liabilities and potential transportation costs.

A consulting firm, Landauer Associates, examined "subjective data" -- such as the educational standards of a given locality and the locality's experience with and willingness to accommodate a racially integrated work force.

Landauer filed reports on 54 localities, according to GM sources.

Finally, GM did another set of computer runs, this time looking at "cost-specific data" for individual sites -- focusing on matters such as energy and other utility rates, site-development costs and local taxes.

Argonaut officials reportedly visited 30 sites that were subjected to the final "cost-specific" analysis. GM's top executives, including Chairman Roger B. Smith and President F. James McDonald, reportedly visited about 15.

The findings from all of this research has been sent to Saturn Corp.'s key officials, who soon are expected to make final recommendations to GM's six-member executive committee, GM sources said.

"We've never gone through and made any formal listing of 'most favorable sites,' " one GM official said. "But there are a number of guys who sit on the site-selection task force who have strong feelings about which site should be chosen."

GM sources said that the infighting on that committee sometimes has spilled over into print with leaks about "leading candidates." Those sources say internal jockeying has reached a fevered pitch now, particularly between the Michigan and the Texas advocates, who are trying to score final points before the executive committee renders its decision.