Could you take a picture of the fit around the motor mount and what you cut. And is anyone running the 2 1/4" Hooker Dual exhaust system i have a 350/700R4, and I plan on running that with a set of Flowmaster 44's.
Sorry, I can't take a picture because I removed the small block and swapped in a big block. I did buy Hooker headers again if it means anything. I will say it was pretty minor in a useless area of the motor mount. Took 2 minutes with the sawzall with the mount in the vehicle. Drivers side, upper rear corner of the metal mount that bolts to the block. It might not be necessary with all mounts. The tolerances seem pretty sloppy on the outside of the mounts.
Also, I am currently running the hooker dual 2 1/4" exhaust. I had it with the small block and modified it with the big block. I think it is a great deal. Fits fine and bolts in with the hooker headers. I think you'll be happy with it. And you can rotate the intermediate pipes around a tiny bit before you clamp them to be sure and clear all your drivetrain and stuff. Rear side exit, and I was able to tuck it up under the quarter panel pretty close to it never get's hit when wheelin'.
With that said, I will probably convert to bigger tubes with my big block eventually.