OK...tach in just this AM and I'm running about 60mph at 2700rpm in 4th gear... seems to be smoothe and happy

Thanks again to all who chimed in...
Dodari: I'm betting that at 3650rpm you are over revving by about 600...at least according to the numbers posted here before but I'm certainly no pro. Put that 355 diff gear in and you will be better off.....IMO..