4 Barrel on 273?

If buying a manifold, I'd try for the good used LD4B intake. They're still available from time to time, and good flow. They really open up the 273, plus the original 4bbl air cleaner will still fit under the hood with no problems.

Unless its cam'd and sprung for a 4bbl, Sticking to a smaller 500-600 CFM Carb is about max fuel you could dump.

The edelbrock performer seems to be a pretty close duplicate to the smog edition 318/360 4bbl. I wasnt that impressed with it.