i am not looking at a calculator, but going 120 at under 3000 pounds can’t be more than 450 horse or so.
With those heads and 500 inches it should run low 10’s at that weight. Not trying to pick on ya bro, just saying what I think.
My 10 to 1 360 with mildly ported Eddie heads went almost 119 at 400 pounds heavier than your car is.
Not sure what the issues are, the convertor though is killing lots of ET, I guarantee you. Nice looking car you have, she is a beauty.