Virginia Republicans jubilantly approved a proposed $720,000 fund-raising plan for next year and cheered Gov.-elect John N. Dalton yesterday as he promised to work for election of more Republican legislators.

The Republicans' central committee meeting at the Marriott Twin Bridges Hotel here was in sharp contrast to that of disillusioned Democrats whose central committee met yesterday in Richmond.

The Republicans completed plans for their state convention, to be held June 2-3 in Richmond, by agreeing to a plan that will apportion 3.081 convention delegates among the state's 10 congressional districts.

The plans apportions delegates on the basis of votes received by President Gerald Ford and Dalton in 1976 and 1977.

Under the formula, the state's most conservative political regions, the south side of Richmond and the Shenandoah Valley, will have gained proportionately greater representative at the convention than will the more populous Washington suburbs or the Hampton Roads area.

The Republicans did not express surprise when they learned that the Democrats had voted yesterday to hold a convention rather than a primary to nominate the party's 1978 candidate for the U.S. Senate seat of Republican William L. Scott.

"I don't think it will make any difference," snapped Republican Party chairman George N. McMath, refering to the Democrats' decision. "They'll still be nominating liberals. The die is cast."

McMath also predicted that the Democrats may have difficulty "just logistically - finding a place to meet." He said Republicans had to book their state convention a year and a half in advance in order to secure a building, the Richmond Coliseum, large enough to accomodate the delegates.

Dalton said he was not surprised at the Democrat's decision. "They've been tearing themselves to death for years with their primaries," he said. He declined to predict what type of candidate the convention would be likely to endorse.

Dalton and Attorney General-elect Marshall Coleman met privately yesterday with their party's delegations from the Virginia House and Senate to brief them on top-level appointments Dalton plans to announce Monday afternoon in Richmond.