A 650 is too small. A 750 Double Pumper would work much better. Also a 904 would net you .4 to .5 in E.T. and around 5 mph. I went through almost this exact same situation that you are now and switching to a 904 just about floored me. I went from 12.92 to 12.46 in a weeks time. At around that time I went from a 650 DP to a 750 DP just before the trans swap. It went from running 13.20s@99 to 12.90s@103. Then it ran 109 with the 904. I say if you have the ability to go 904, do it, you wont believe the difference.