See if autozone will let you take a drive with one. Like a month or so ago I convinced them to let me install and drive off with a MAP sensor to see if it would solve my problem haha.
I've been looking into this some and while some of them are probably just ignition issues more and more points to the possibility of some being a PCM or transmission problem. Here'* one bit I found on thrashercharged.com talking about a 65-e shiftkit:
"Over the winter ('9
, we've been working on this and determining the best and most cost effective way to address these issues. We've concluded that there is no easy way to modify the shift points or shift schedules / patterns, and modifying TCC lockup is not as simple as it was in previous years due to the introduction of the ECCC (Electronically Controlled Clutch Capacity) system, where the pressure plate does not fully lock to the torque convertor cover.
Instead, a special material is used in the clutch lining that allows a small amount of slippage to constantly occur, allowing the TCC to be ramped in and out slowly, reducing driveline torsional disturbances and eliminating TCC shudder or chuggle, two common complaints in the past. "
While it isn't specific it does say the "TCC shudder or chuggle" was a common complaint and that changes in the transmission eliminated it. This mounted with the other bits I think makes an issue outside the ignition plausible. Don't go throwing parts at it yet though, still much to be learned.