In an early test of Republican grass-roots sentiment, Gerald R. Ford emerges as the top choice of Republican voters for the party's presidential nomination in 1980, winning 40 percent of the vote to 30 percent for former California Gov. Ronald Reagan and 11 percent for Sen. Howard H. Baker Jr. of Tennessee.

Tied for fourth place with 4 percent each are Elliot L. Richardson, Kansas Sen. Bob Dole and John B. Connally.

With speculation mounting that Ford will seek the GOP nomination in 1980, the Gallup Poll included his name on a list of six prominent Republicans in this early look at the 1980 race.

The latest findings show a gain for Ford since last September and undoubtedlt reflect his increased media exposure and activity on the speaking circuit.

The list of Republicans used in the September survey was considerably longer. At that time, Ford trailed Reagan.

In the latest findings, Ford also leads Reagan among Republicans when the two are matched head-to-head.

When asked which man they would prefer to have the 1980 GOP convention select if the choice comes down to Ford or Reagan, 54 percent said Ford and 42 percent Reagan.

Jimmy Carter was almost unknown outside Georgia two years before the 1976 Democratic primaries. If White House aspirants learned anything from Carter's rise to the presidency it is the value of early and intensive campaigning at the grass-roots level.

The latest poll shows that only a half dozen of those Republicans mentioned as possible nominees in 1980 are known to a majority of their party members.

Ford and Reagan are known to virtually all party members. Connally, with an 82 percent recognition figure, ranks about even with 1976 vice presidential nominee Dole, whose name awareness registers 79 percent, Baker, at 65 percent, and Richardson, 53 percent, are the only others known by more than half of Republican Party members.

The following questions were asked:

Which one would you like to see nominated as the Republican candidate for president in 1980? (TABLE) Fort(COLUMN)40% Reagan(COLUMN)30% Baker(COLUMN)11% Richardson(COLUMN) 4% Dole(COLUMN) 4% Connally(COLUMN) 4% Undecided(COLUMN) 7%(END TABLE)

Suppose the choice for president in the Republican convention in 1980 narrows down to Gerald Ford and Ronald Regan. Which would you prefer to have the Republican convention select? (TABLE) Ford(COLUMN)54% Reagan(COLUMN)42% Undecided(COLUMN) 4(END TABLE)

The results are based on personal interviews with a sample of 1,574 adults, including 363 Republicans, 18 and older, interviewed in more than 300 scientifically selected localities during the period March 31-April 3.