[jimfulco]

I wouldn't use a Performer on a stock or nearly stock 305. Too much volume in the runners that you can't use, and which can diminish the signal to the carb, causing poor driveability and, I suspect, gas mileage. The Performer reduces the performance of even a 350 up until 3000-3500rpm, according to an Edelbrock graph I saw a few years ago. Bigger is not always better.

EGR or non-EGR depends on carb calibration, and vice-versa. Disconnecting EGR with a carb that's calibrated for use WITH it can cause pinging at part-throttle due to a lean mixture. You can recalibrate the carb to be a little richer at part-throttle, and the pinging will disappear. EGR is not in the circuit at full-throttle, so WOT performance might not be diminished by it, but part-throttle efficiency is a different story. I'd be tempted to use a pre-'73 intake and carb, if possible, just to keep away from EGR problems.

Be sure of a couple of things when you go to pick a manifold. Does your air conditioner compressor use a rear brace that mounts to two holes straddling the crossover port on the driver's side of the intake? Not all intakes have those holes. The alternator brackets have a rear hole that mount to a hole near the top front of the intake. Early long-water-pump engines had the hole in a different place than the later ones. This may be addressed by getting an alternator bracket that matches the intake. The changeover was sometime in the '70s, but I don't know which year. I found a late-style non-EGR cast iron intake without EGR but with A/C bracket holes on a '77 Chevy van.

I'd be a little leery of the factory aluminum intakes, what with the fine quality control they had back then. Not to mention they didn't use any kind of anti-seize compound when they bolted stuff to them. Check all the bolt holes for threads, and hope like heck it's not warped.