Converters are nice, just need to tune for them and get a healthy tranny cooler......and decent tires.
I loved my Yank 3600 for DD but i dont mind my Circle D 4000 either just wish i had better tires for it for the street. BTW my 10bolt is still holding up (knocking on wood)
Another thing too my stock rebuilt 4L60e lasted only a year with the yank and it had a cooler, jus sayin