I recently did this. Got a set of GT/CS mufflers for $20, cut off the pipes going into the V6 muffler and had it expanded to fit the V8. Cut the inlet pipe off the V8 mufflers and used the modified V6 inlet pipe. Fits perfect, slight increase in sound and love the rolled tips.
'13 Premium Ingot Silver V6
'92 Coupe MM catalog 552rwhp Kurgan tuned