So, I'm second thinking a single in/dual out Flowmaster. Eventually I'm dropping a 318 in so why not just have the exhaust ready, and not waste money on a single in with dual outs that will be scrapped in a year or so anyway?

How different is a V6 muffler from a V8? I planned on running them as straight as possible for the best sound, I've even heard of people cutting holes in their frame etc to maintain a straight pipe all the way back. My theory was drop the exhaust from the headers back, have the fittings welded onto the two pipes that bolt up to the headers. Bypass my cat until the cops give me a problem or getting a sticker becomes a hassle then I'll invest in high-flow cats but do I really need them?

 

If you get a nice single in-dual out system built, you shouldn't have to scrap it if you swap engines. The only thing to keep in mind is what muffler and pipe size you choose. If you plan on doing a 318 swap, just pick a larger pipe size and muffler from the start.
If your frame looks anything like mine does, I'd reconsider cutting holes through it.
If you have emissions to pass, you'll need your cats. High flow is a good option.

 

I'm just going to stick with the normal size pipe, I don't want this exhaust on my V8. If you have 4 cylinders per pipe, then use it to your advantage. I was thinking about gutting the cats and welding pass-thru pipes right through them so they appear to be a working cat but it's nothing but a straight tube inside.

 

just gutting the cat will do it. Just dont beat on it too badly and it will stay solid, then you have a resonator from factory! lol

 

Wouldn't that create an expansion chamber though if I gut it without a straight though pipe?