Big engines are sensitive to restricted exhaust flow. On a Pontiac 455 in a 4x4 Blazer that the dude insisted on using the column shifter, I had to use factory exhaust maniifoolds. It literally KILLED that engine! I bet it loped off a hundred HP and that much torque to boot!
On the same engine I had used 3" Flowmaster 40's w/an H pipe connecting the two sides. Had turndowns about a foot long out the back of the mufflers. They ended right under the rear seat area.
This was in an '81 Camaro. You'd have thought the droning would have been bad- and it probably would have been, had I not used heavy factory-type insulation (tar/felt type) scavenged from junkyard vehicles.
About the best thing that could be said for it was it wasn't very restrictive. But it would set off car alarms just idling through a parking lot- which was something I enjoyed doing where the ricers congregated in the K-Mart parking lot on W. Colonial Dr. in Orlando on weekend nights. Not so enjoyable while driving through residential neighborhoods, like my own.
But it ran great. Effortless 12's w/a 3.08, lower 12's w/a 3.31 rear gear.
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That said, no good reason you can't tune the Edelbrock 750 to work. I don't much care for the non adjustability of the secondary opening rate, unless it's a Thunder series carb.