A couple of small points for you after you have tried most of the above:
1 Check that there is a breather in the fuel filler cap , it is just possible that the wash has clogged it with dirt (not likely I know , but i have known it happen)
2 You mention that the car had lain idle for a while. When this in the case it possible that the gasoline goes "off" . Again it is unlikely but IF all else has failed that try draining down the tank and refilling with fresh.
A couple of other questions:
Are you using the standard mechanical fuel pump? Or has it been converted to electric at some point. If the former try emptying out the fuel filter bowl and then seeing how quickly it refills. If the latter are you sure that the pump is delivering fuel to the carbs , try disconnecting the fuel line at the carbs to test a good delivery.
Secondly is the ignition system standard, to has water got into an electronic module which may be mounted on the inside valence near the front.
Are you sure that the distributor is in exactly the same spot and not been accidentally knocked.
Good luck
