Need some advice on Exhaust and Headers

[almcbri]

Well I was introduced to a guy that said he would do all my exhaust fab work and build a set of headers for my 68 camaro for no charge. I am doing a little trade out work.
This guy does some amazing work. My question is: What type of mufflers should I go with? what size? I had 2.5" on before. I am going to keep the mufflers kinda tucked under the rear where they aren't too visible. I am up for any input, or creative ideas. This is not my area of expertise!

As far as Headers go, I am not sure either: Would I be better off to buy a set or have this guy build a set?
I appreciate any help.

Scott, I was kinda unsure which section to but this thread in, so feel free to move if you need to.

Thanks, Andrew