ok the time is coming soon to rebuild my trans what are the best gear ratio's for a saginaw mated to 373 gears

The factory st10 in my 77 has 2.64, 1.75, 1.34, 1.00. With 3.73 in the rear it seems very good to me. Some of the trans am t10s have very high 1st gears (I forget off the top of my head, 3+ ratio) that may be a bit much with that rear.

A ST-10 is a Borg Warner and not a Sag.

yup i made a mistake its clearly stamped on the trany

My T10 has the higher gears. I pull through first like its not even there, second is the same. If Im on it. Im redline in first at 30-35mph, Second at 45, third at 55-60 and fourth, I dont know needle pegs at 85mph and Im about 4k rpms.