I'm still new at all of this, but I just installed a similar setup in my challenger, using the stock tank and a 3/8" sending unit. I mounted my pump at the "tow hook" at the frame rail, very close to where yours is. However, I think I mounted my pump higher, and there shouldn't be an exhaust clearance problem, but I might run turnouts or side exit anyway. I got a carter electric fuel pump that is loud as hell, but doesn't seem to have a problem pushing the fuel.
Has anybody measured the clearance from the tank - tailpipe - frame rail?