Which 3" tailpipes?
When I bought my 3s from TTI,for my 68 Barracuda,I bought a complete kit front to rear. They told me they were for a 111wb, and sure enough I had to cut some out from the fronts. Not knowing where I would have to section the pipes,I installed everything from back to front. The 3s are a very tight fit between the tank and the framerails, but with a little ingenuity it all fit.I bought the ones with the turn-downs; That was a lucky spontaneous decision, as when the salesgirl asked me, I didn't even know there were options. I just blurted the choice out without aforethought.And yes dual 3s are fairly loud on my 367, but the Dynomaxers make the scream bearable,and I have never in 14 years been given a citation for noise.
I have stock tubs, and my springs have been moved inboard a bit,close to 3/4 inch per side.