can you cut and weld yourself?
if so, do what i do:
make 8 vertical slits down the inlet of the exhaust tubing. if you use a metal blade like a sawzall/reciprocating saw/bandsaw, the slits will be about 1/8" wide. if you use an air powered cut-off wheel, they will be slightly wider since the disc tends to remove more material.
once you made these 8 cuts, lay the exhaust tubing down on a piece of wood or bench vice, etc and gently tap the end of the freshly cut tubing to carefully close the gaps between the cuts. the cuts should only be about 1/2" deep from the end of the tubing. if you want a longer transition, make the cuts longer, like 3/4". of course, youll have to weld more to seal these slits back up.
basically, you are removing material to taper down the end of the tubing to the desired inside diameter. if the intial cuts dont remove enough material from the circumference of the tubing end, simply re-cut the slits after youve hammered and tapered the end down to a smaller diameter; then hammer more and increase the taper to an even smaller diameter.
ive done this to put a 4" WOTM down pipe onto an SP turbo with 3" V-band. ive also done this to make my own slip-joint to avoid having to butt-weld exhaust tubing. if you have the welder and the cutting tool, its just your time. you can do it in an hour.
