Mark is right - You could have several quarts of water in the bottom of the tank - and that water can put some ugly stuff inside the fuel line.
So if you want to get it moving NOW - (and need a fuel supply) drop a temporary rubber line off the suction side of the fuel pump into a gallon plastic fuel can or similar vessel. Fuel pumps don't have much suction - and the stuff its sucking isn't what you want in the engine anyway. If its the variety of fuel pump with a filter on the bottom - take care of whatever gunk it has in it.
Get some shop towels and a couple of cans of spray "carburetor cleaner" and wash down the carb so things are easily moved - looked at - adjusted, etc. If you can drain gunky gas that may be in the bowl already - do it. I've taken them off ranch trucks just so I could invert them and blast the throttle bores with more carb cleaner from the "down side". Don't leave a lot of "potential fire" lying around on the top of the manifold.
Take off the distributor cap and have a look - more shop towels and a can of WD40 is the trick here. Just clean it up for a start - and look for wires so old they may short - my bird had 50 year old (cooked) wiring and the insulation fell off everywhere you touched it. Be cautious - you'd like the thing to make sparks for a few more minutes anyway....
If you can - drain the sump and add some oil - get the water out of the crankcase. You don't have to change it all sight unseen - but you want good stuff in the bearings right away and to put some warm in there - so you can really change the oil sometime the first day.
If it turns out you need a new fuel pump - get one off a 60's/70's FE truck motor that has the canister style filter housing on the bottom. Makes this fuel line / tank cleanout a little easier to bear.
Steve Metzger Tucson, Arizona