How the transmission holds up depends on how you drive it.

Saginaw Ratio's

Number of ID Grooves
..............................1st 2nd 3rd 4th
No Grooves...............2.84 2.01 1.35 1.00
1............................2.54 1.80 1.44 1.00
2............................3.11 2.20 1.47 1.00
3............................3.50 2.47 1.65 1.00

Muncie Ratio's

Suffix 1st gear ratio
A 2.52:1 wide range
B 2.20:1 close range
C 2.20:1 Rock Crusher

What's nice about the Saginaw transmission, if you get a 2 or 3 groove (this is grooves on the input shaft) you can run a taller rear end gear.