http://chevy.oldcarmanualproject.com/chevyresto/52152.html

First 2.94 : 1
Second 1.68 : 1
Third 1 : 1
Reverse 2.94 : 1

I've read you want a factor of 9 to 9.5 for street machines for first gear.
Using above ratios, 9.5/2.94 = 3.23 rear axle ratio.
Tire diameter plays a factor as well.

For 60's Saginaw 3 Speed:

# of shaft grooves 1st Gear 2nd Gear 3rd Gear

0 2.85 1.68 1.0

1 2.54 1.50 1.0

2 3.11 1.84 1.0

3 3.50 1.89 1.0

reverse is 2.95

A 2.73 rear axle with 2.85 first gear = ride clutch to get moving.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."