How to identify what came with car

[gtxno1]

Hello everyone just picked up my project 70 cuda how do I know what gear ratio actually came with the car decoded the tag and vin nothing thanks

[anlauto]

That information is found on the broadcast sheet. If you have one.

[Floyd]

If the rear end hasn't been messed with it should have a gear ratio tag on one of the carrier studs.  Example pic snagged off the web

[R/T's 4 R/P]

If the tag or broadcast sheet is missing or cannot be read, there may be certain clues.
What is engine size? What size radiator? Power brakes? Etc.

[YYZ]

Also, if it is a non-A/C, non-340 car, then the rad cradle will help to narrow things down.

22" rad - most likely 3.23 gears (383-4, 440-4/auto, 440-6/auto)

26" rad - 3.55 or 3.91 gears (383-4, 440 auto) unless it was Dana equipped

26" 440-4, 440-6

- if automatic, then 4.10 Dana

- if 4 speed, but with manual drum brakes, then likely 3.54 Dana

- if 4 speed with power discs, then likely 4.10 Dana

[6bblgt]

if NO axle package is on the fender tag of a '70 'cuda (BS non-AAR) = 3.23:1 ratio & 8-3/4" rear axle

[PLY474]

I often refer to the AMA Specifications.
https://www.hamtramck-historical.com/ama/_1970AutomobileManufacturersAssociation-01.shtml?load_img=1