It depends on what carrier you have. Pull the rear cover and get the facts and then you will know what the best plan of attack is.

If you have a number 3 carrier you can go all the way down to 3.08 gears...

Here is some more data for you from: http://richmondgear.com/07Apdfs/page27.pdf

GM 8.875 12 bolt rear ring and pinion data.

RATIO PART NO. TEETH CARRIER
3.08 49-0068-1 40-13 3
3.42 49-0070-1 41-12 3
3.73 49-0072-1 41-11 3
3.73 49-0280-1 41-11 4
4.10 69-0204-1 41-10 4
4.10 69-0350-1 41-10 3
4.56 69-0206-1 41-9 4
4.56 69-0352-1 41-9 3
4.88 69-0298-1 39-8 4
5.13 69-0300-1 41-8 4
5.38 69-0302-1 43-8 4

In the Stovebolt Gallery ~~ "The Orange Crate" 1965 C10 SWB Step Side Build Thread

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