On my 1966 38 Express, I have two large .75 litre sized filters, brass cases and tops, with a replacable cartridge filter inside, one dedicated for each engine.
These are Groco brand, and look original. The fuel line goes directly to the fuel pump, and then into a final filter that is nothing more than a pencil sized screen held vertically inside a small aluminum case about the size of those mini cans of tomato juice.
This photo below is for a 283F, but the 427 has the identical same final filter you see under the word "GOODYEAR". If that is all the filter you have, you are WAY underfiltered (and they are probably clogged).
Here's what the 427 version looks like (Bill Mulvey's CHALLENGER)
I recently disassembled one identical to the one in the photo above, and it was half filled with rusty sediment. It is only good as a final filter, but on my 20' Sea Skiff project boat that's the only filter on board. I promptly added a big Racor, because I know that even a little spec of debris can screw up a carb.
I'd take a look at the filter, if it's really dirty I think you may have found the issue. Carbs may need to have all the needles backed out and carb cleaned, perhaps blow out with air, may not need to disassemble.
Groco filter link for reference
http://www.network54.com/Forum/424840/message/1170748099
Regards,
Paul