Ok, I have a healthy 454 in a '68 with a Turbo 350. The motor is producing somewhere in the neighborhood of 600HP according to desktop dyno. I just put this tranny in which I bought from a close friend that I trust. I replaced the tranny because the TH350 that was in it seemed to be slipping in 3rd gear and very slow to shift from 2nd to 3rd and also had a lot of clutch material in the pan and since I didn't really know the original condition of this tranny I figured it was just spent. I had my 3500 stall split and cleaned/inspected at my local tranny shop as to preclude introducing any previous clutch material/garbage into newly rebuilt tranny. Well This tranny seems to be OK but it still wants to slip a bit in 3rd gear when I power up. Seems to hold OK in 1st and 2nd, but when cruising down freeway and romp it tach climbs to about 5K and feels like slippage again. Also still slow to shift from 2nd to 3rd. Common factor to both situations is that passing gear linkage was not hooked on either. And same torque converter. I've heard that passing gear cable has an effect on pressures in the TH350's. Any tranny experts out there have any advice?? I know that this tranny isn't really built to handle this kind of power but I'm saving my pennies to buy a really built one from TransKing or ATI or someone like that. Is it possible that I just have too much motor for a stock TH350?? I figured it would be ok for a while but just wouldn't last that long. I have a feeling it is something simple right under my nose and I just don't know it. HELP!