I have a TH 400 in my 68 behind a 454 and a 2500 stall conveter. When left in drive, the shift point from 1st to 2nd happens very fast, just barely out of idle speed (1500 RPM) unless I really hop on it fully. I find if I want to drive at all aggresively (god forbid) I have to shift gears by hand. Why would this be. I have a shift kit installed (B and M I think).