2.5" vs. 2" exhaust

[parb]

Hi all,

i'm in the final stretch of restoring my 72 GMC Jimmy. I have gotten from a member here a set of nice ram horns for the engine.
My plan is to drop them down into a 2.5" exhaust system with borla mufflers (i have borla's on another car and i like the sound, plus i like the guy behind borla -chatted to him and he is a real nice guy).

I'm not the best mechanic so i am having a mechanic help me out. he told me earlier today that going for a 2.5" exhaust may not be the best, and that those old 350 chevy v8's needed a bit of back pressure to run right. He suggested 2" as the right size for my exhaust.

Everything i've read on this forum suggest that 2.5" is a good choice for this engine.

What do you all think? Am i making a mistake going with 2.5" inch exhaust from the ram horns all the way to the exhaust tips and i should really make that into a 2" exhaust?

I still have some time to change my mind if that is the right choice, but i would love your inputs. especially those who have put on a 2.5" system.

My engine otherwise is bone stock.

thanks!