I have a 67 Elky w/327 and about 60mph or so the engine starts to fall over like the carb is being choked (choke's fine) or not enough fuel getting to the carb. Doesn't pop, buckle, etc. just falls flat. Increasing the throttle does nothing. I recently had a problem with the fuel tank not venting (thread http://www.chevelles.com/forums/showthread.php?t=167836). Fuel filter is fine and carb seems to be OK. I'm wondering if the fuel pump diaphragm might have gotten messed up. I don't see any gas in the oil like before but I quit driving it after this happened.

Suggestions?

can you rig up some kind of fuel pressure gauge? That will tell the story.