Back seat will not fit without modification. Blownfish is the only person I have seen so far that is running a backseat after a minitub on an early Barracuda. I'm sure you can search through his old posts to find pics. He had to remove and disassemble the seat and also cut some of the framing out to be able to do it. The seat bar brackets will also need relocated if you want to maintain the original angle. I'm currently minitubbing mine with the plan to do the same, but I'll probably never reinstall the back seat. If I do, it will be the last project after everything else is done.