Thanks for the tips! I have a recent distributor with a pertonics module, new ballast resistor, new coil, recent plug wires, newly rebuilt alternator, new regulator. I am going to get a new set of plugs too for good measure. Like I say I will check the timing once more as it's been a little while since I last did that. Carb is a carter BBS, I just gave it a thorough cleaning and noticed the float was out of adjustment, so I fixed that. Got the lid to seal up good on that too. The carb is getting tired, I need to swap to something else someday but it seems to be behaving well. I have a decent set of mechanic tools and have access to tools from a street rod builder, so tools themselves shouldn't be an issue. I have a decent amount of experience with engines and with this engine, which is part of why I am so frustrated. Like I say, I have been through this engine and man does the car lurch when I let off the brake when it's warm that made me migrate to thinking transmission, but I can easily be wrong. I'll try to take a video where I make the symptom arise & we can hear the engine & see the tach.