big let down car will not move now

Man, I would have bet a donut that it was the fluid level, ie. let the car idle in N for about 30 seconds before R. Thats an old Gil Younger trick (tranny guru) he has a kit that stops the convertor from draining back called the 'no yo-yo" kit. Its just a different spool valve that prevents convertor drainback in P. Good catch.
I always heard using open ended nuts on longer studs anyway. NHRA does too.