2.5 or 3 inch exhaust, 351C

[a70stang2nv]

Here's the deal. i have a 351C, edelbrock heads, bored 40, with a 505 lift cam. and all the other goodies but enough to understand. reputation of the cleveland is that it has large valves and back pressure becomes an issue. i'm hoping to find someone with enough experience to know which is better for performance on this engine, 2.5 exhaust or 3. i know alot of ppl may fuss over this issue but i want to get this perfect without wasting the money figuring out which is better. please reply