In the 66 Cutlass if the rear is original it would most likely have the BOP 8.2 rear. The one from Summitt appears to be the correct unit for that rear if it lists 1966 as included. See notes also about ring and pinion gears able to be used ...

 

ring and pinion gears will fit.

Thank you!

 

try to get one with 30 spline side gears for more strength.

 

of course that will mandate new axles.

 

Well first off you need to see what ratio you are going to use.
I ID-ed your rear diff picture as a PONTIAC 10 bolt 8.2 rear end which is common to be in a 66 67 Olds.
The unit will fit 2.93 3.08 or 3.23 ONLY ratios. 113 (auburn) end three digits will fit the 3.36-4.33 8.2 gears.
I can beat these Summit prices all day long and the 3.36-4.33 we can get you as Eaton posi better than the Auburn...
3.55 3.90 gears we have on the shelf also. All 8.2 Pontiac gears are a bit pricey again sure I can beat the Summit prices up and down.

Look on the edge of your ring gear to find the stamped in numbers...List them and will decode the ratio for you. Jim

JD

 

hi,i have a '66 88 with the 425 with the 400 and open rear.i probably have the pontiac rear end too.there's gotta be some posi units available for this.monzaz,an we talk rears?..thanks ..paul