Sidepipe muffler flow for 700bhp

[Ant]

Mufflers for 700bhp, with running a 373 sbf engine producing almost 700bhp, I have read where a 3" perferated core muffler will give probably the least restriction, I wonder whether 3" id mufflers are big enough for large hp race engines, so thinking of going 3.5" mufflers but I will need to go to 4.5" outer case to get some room for the stainless steel sound proofing material?

A friend has made some mufflers for his 390FE Cobra with 2" primaries going to 3.5" collectors, but then down to 2.5" perf core muffler insert, although his engine doesnt rev that much over 5500rpm its damn noisy. I reckon a larger core may quieten more, and the core size may restrict his performance.

Anyone with high revving small blocks have any recommendations, I thing I am at the limits of a 3" core muffler, of course there are design issues pending how good we have the headers and they scavenge we will find out in a few weeks when I dyno the engine and try a few combinations.