65 cuda exhaust pipe size?

I will go back with oem style for 273 4 bbl setup. what size pipe is the exhaust pipe? i'm thinking the pipe from exh man back, the y pipes, and to muffler was 2 1/4 the out from muf was 2 1/2?????
I have local guy bend the pipe, he has a real hard time with anything bigger than 2 1/4 where it leaving the exh man.

this is driver, no racer. and buying stuff like mandrel bent tti stuff is NOT on my plate!!! LOL thanks for any info.