Were the original style e-body mufflers (2-1/4" in, mounted beside the tank) a straight through type of design?

I have a pair on my Challenger but they are welded in place (no resonators).

I am curious how much of a performance gain there would be in swapping these 2-1/4"-2" muffler/R/T exhaust tip assemblies out for an aftermarket 2-1/2" straight thru muffler with 2-1/2" R/T tips since I now have headers and 2-1/2" pipe up front before the start of the 2-1/4" tail pipe assembly.

Any thoughts?

Thanks