69 Caprice with dual 3" with an X-pipe. I run Hooker Super Comps (huge) and they don't fit the best. And to top it off they hang down quite a bit. But, I knew what I was getting into.
I had my 3" exhaust fabricated at a speed shop. They used all mandrel bends (no kinks). My crossmember is also fabricated, so I can't help you there. The X ended up about 12" behind the transmission mount. I used Flowmaster 70 series (large) that made everything a tight fit. The exhaust runs all the way to the bumper. The car is pretty quiet, but has a nice tone to it. Years of running super turbo mufflers with dumps made me want something quiet (and that didn't rattle the interior or my head) driving down the road.
I did try a 3" bolt on kit...It was from Torque Tech (several years ago), and it didn't fit what-so-ever. So, go with a recommended kit.