I need a fuel pump for my 454 for my 79. I can get a fuel pump with return lines, but then what do I do with the vapor return line? I don't really want to put the canister back in just for a vent line.

I could also run an older fuel pump without the fuel return or vapor return line, and just run a vented gas cap. However, 70-74 gas caps, which are vented, have a different thread on them then the 75 and up cars do.

Can anyone give me a part number for a vented gas cap that will fit a 79 or tell me what to do with the vapor return line if I don't run the canister?

i just left that vapor return line open

I done the same on my 88 camaro.

Stock it had 3 fuel ines.
1 supply
1 return
1 vapor line

I put on a return (3 line) mech. pump, and ran the stock supply and return lines to the pump, and just left the vapor line open