Flowmaster drone solved.

Bryan the 17748 is a 20" body muffler and stock uses 18" ones. I shortened the inlet bushing 1" and then welded three bolt flanges to the outlet bushing that had also been shortened. i also welded flanges to the tailpipes so instead of sliding in, they bolt on. They all fit fine and sound great.
I love the Helmholts tunable resonator pipes listed above too!