OP, there should be a factory spec sticker in your drivers side door jamb. It will list options and then directly underneath the options name will be a code. We need the code under the word "Axle". That code will tell you what rear axle ratio you have.
You can compare your code on your sticker with the codes listed below
click here for axle codesI fully believe that you are going to be just fine... hopefully your code is H9 (for 3.55) or B6 (3.73) both with limited slip.
BTW.. a half ton should have 1000-1500 lbs of payload. Most of the half ton trucks back then were regular cabs. Not heavy payload eating crew cabs like we have now.
Thanks!
Jeremiah
