WHATEVER GRAND DESIGNS may some day be ratified to finance Greater Washington's Metro system over the long run, it still relies today on perodic, hat-in-hand tours through the various government for stop-gap contributions. At this point, the attention is on Virginia, where it looks as if at least some help may be on the way. Though Gov. mills Goodwin hasn't announced any sudden, newfound love for the subway, he has won the highway he wanted (I-66 and all that) and will no longer hold the subway hostage. Morever, as a result of the I-66 agreement now reaffirmed by Secretary of Transportation Brock Adams, the governor apparently is committed to turn over some federal highway money to Metro, as well as a right-of-way along the I-66 corridor.

The question now is just how far Gov. Godwin intends to carry any spirit of cooperation. Last year, as you may recall, he vetoed a $10-million appropriation for subway contruction. This budget item is again under consideration in Richmond: Yesterday, the House of Delegates approved it. If the state Senate also recognizes its importance, Gov. Godwin should see fit to let it go into law this time.

There's another Metro-related legislative revival in progress in Richgmond: The Senate approved a measure yesterday that would permit Northern Virginia jurisdictions to impose - individually - a 4 per cent tax on gasoline sales to help pay the region's Metro costs. This tax was approved last year but with a hooker: It could not be imposed unless all the local governments involved approved it: Fairfax City didn't. The revised measure deserves enactment.

At the local level, Alexandria this week joined other area governments in approving a financing plan to pay for at least the first 60 miles of the proposed 100-mile Metrorail system. The District of Columbia and Prince George's Country have yet to sign, but apparently there's little objection in either place. Approval does not - and should not - imply agreement on a truncation of the larger rail network. That decision will depend on a whole set of questions still be answered on the federal, state and local levels.