So.. Big engine rebuild is done. I watched the break in process and all ran fine, all rev'd fine.
Install engine in car, fresh wiring for grounding off the block, to the body and to neg terminal on battery. I noticed I was getting a small pop/misfire out of the carb once load was put on it. You can rev all day in park or neutral, once you put in drive, it pops cries all day. I do have a MSD 6AL box in the car. There is no vacuum advance. Cylinder pressures verified, timing is good... sits at about 36 on the advance. Mechanically, nothing changed from breakin stand to car..Vacuum leaks are non existent, as there are only 2 active vacuum ports. Checked cylinder head for leaks and we are good there. One for brake booster and one for trans vacuum modulator. I plugged the modulator to see if this was the issue, no joy there. I do have a B&M Star shifter in the vehicle, and it requires neutral safety switch and reverse light switch. I am at a bit of a loss to looking for this issue. I am pretty sure it is electrical. I think I am going to bypass both switches for testing to see if the shifter switch is failing. I find no mention anywhere of the shifter itself need to be grounded. It is not mounted to the trans tunnel, but on the carpet over it.

Anyone want to help with my gray hair problem?
Thanks in advance!
Drew