pontiac rear end question

i got a 50 poncho and i need to get schooled on ratios, this is what i got from the shop manual:

Syhchro-Mesh Models

designation ratio axle color

plains 39:10 Red


what does it mean? i got a sbc hooked to a overdrive ******? im i good or it the rear going to be streaming every time i get p*** 50?

 

With a overdrive ... you should be good to go ...

A 3.90 ratio in overdrive ( 30 % ) is 2.73