You're deep into the "overkill' zone on pipe size. My 1970 Cadillac Fleetwood with a 472 cubic inch engine used one 2 1/2" exhaust pipe and muffler, and a single tailpipe the same size. The later 500 cubic inch engine that Cadillac used in the late 1970's used the same syetem.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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