Ok, i found that the accell distributor wasn't seating all the down. I pulled it and compared it to my HEI. Seems the tang that engages the oil pump drive shaft was about 1/8" shorter on the accell. I carefully trimmed it up to the same length as the HEI. Put it back in and it seated properly. I also installed a heavier duty hold down clamp with a stud.

Took it out for a test. Ran awesome until i punched it. I actually heard a small knock sound and then sure enough, the engine is missing again: distributor jumped a tooth again! So what gives?? The HEI stays put and runs fine. The accell runs good until you mash the gas... I'm thinking maybe the distributor gear isn't meshing properly with the cam gear. Should i try the gear off the HEI???

On a positive note, i'm really good at swapping distributors and setting timing now!