exhaust pipe diameter for a mildly modified 340

i wonder how often most guys drive their cars past 4000 rpm?
90 mph with 3.23 gears and a 26.5" tire is only 3685 rpm.
90 mph with 3.55 gears and a 27" tire is 3976 rpm.
Now you're getting into facts. Why would you let facts get in the way of a good story? :poke:

using factory option E70-14 would have diameter around a 205 70r14, which is 25.3"
with a 3.23 gear, 4000 rpm is still 93 mph, and 3000 rpm is 70 mph.

The place where its most important for exhaust pipes to handle a large volume of flow with minimal resistance is the race track. Read enough here and anyone paying attention has a pretty good sesnse of who brings their car to a track now and then, frequently, and not at all.
Even for those who want maximum horsepower, IMO too many miss that power throughout the gear is often more important than the peak. More so for those of us with gearing that results in hitting the finish line before the hp peak. IMO maintaining flow away from the exhaust port in the low to mid range is going to bring the most gains. If we can do this without stuffing up the top, even better.