I would think that at best, a 2" tube exhaust would serve best. Some guys have suggested 2-1/4 which I think is too big for a small stock lift cam with stock ports and 340 exhaust HP manifolds.
I have a set of magnaflow straight thru 2" mufflers laying around as well that I could include in the package.

What say ye?

I had a 71 cuda with a 360 and edlebrocks,had 1-7/8 hea ders and 2 in. exaust and was a real screamer

I'm at 2.5" minimum preferably with an H-pipe or X-pipe to equalize each bank.

More is just overkill for your application and less IMHO isn't worth the bother.

Kevin

I believe factory head pipes for 340s were 2 1/4" and your manifold opening probably isn't that big. I think 2 1/4" would be plenty with what you have.

Jeff

i use 2.5 on all my stuff

Whatever size the manifolds exit at and then a single 3" That would sound awesome I bet!

-Kenny

2&1/2" with mandrel bends & as low of restriction muffs as you can stand & resonators (glasspacks) alongside the rear springs will let you run a less restricted regular type muff(s) up front & still keep the noise down to a tolerable level. X pipe too. BEST (tho its $$$) is restricted (quiet) muffs up front and cable or elec cutouts! Constant noise is high school stuff and with cutouts with the money in a neutral parties' hands then 10 seconds later it'll all be over but the cryin (& you'll be richer). they wont know what hit em till you pull the cable/flip the switch!

I would use what you have you will never notice the difference A good 2" or 2.25 would work just fine If you have cam up or headers another matter. Biggest difference I saw was comp cam and headers threw a 2.25 exhaust open cutouts dropped car .3 in qtr

I say 2.25 head pipes at least but preferably all the way back.You could expand your 2" mufflers and run them to save money of you want.
An x-pipe would be my preference.

2.5 minimum on everything I own.

Thanks guys. Going 2-1/4 from the head exhaust all the way back.
This is a bone stock 360 with nothing else other than 340 exhaust manifolds.