Chris - no heat shield any more!
I cut a 4" hole in a plate and welded a 4" pipe about 1" above and 5 inches below in there. Then I welded the 5" stack to the plate. The stack comes out in one piece and there are two bolts that hold it solidly in the bed. I just need a 6" stack that's about 40 inches long now and I'll weld that to the plate after grinding the old stack off.