It really depends upon how well the heads flow.....the 50#s may start running lean around 26#? I think you get caught between volume and pressure on these kinda questions so the answer is an "It depends"
29 lbs...6 consecutive runs. Stock block, stock untouched heads. FP set at static 38# with 101 unleaded 33% alc/water mix. DS showed 4º of retard in the 1/2 shift only and 0º throughout the run. The car weighed in at 3701# with me in it and I had one pass that was 119 mph.