I have that combo but I don't remember if I used the driveshaft for the 8.5" 10 bolt or if I used the one for the O-Type. Over the years I've had both rears under the car with the same driveshaft and I can't remember which one it is, so a length measurement would help me ID it.

 

Go to Denny's driveshafts and find the shaft measurement sheet. Click on measuring diagrams along the left side. It will show you exactly how to properly measure driveshaft length.

http://www.dennysdriveshaft.com/

 

Thanks for the input. I was told the driveshaft from the 8.5” rear will not fit, which sucks because I have 1 in my garage. I’m hearing it might even be a 2-piece unit. If you find yourself under your car anytime soon, if you could grab a tape measure and measure your driveshaft, I would be extremely thankful!

Thanks for the tip. That’s a very comprehensive site. I printed out their checklist and may make that my Father’s Day present to myself...1 hour to crawl around under my car, measuring u-joints, shaft, etc....

 

The "two" piece shaft is original to the at least the 68 442 automatic cars, not 100% if this applies to 69-72 autos? All the stick cars 68-72 used a one piece.

By two piece I'm describing a smaller diameter tube which is press fit into a larger diameter tube with a thin rubber sleeve between the two tubes. This was Olds engineering attempting to extract the smoothest ride possible from the automatic cars. They are easily twisted out of phase, especially with more HP/TQ, age and aggressive shifting automatics...ask how I know. Once out of phase they are junk and need to be retubed with a single tube. So if you find a two-piece verify proper U-Joint yoke phasing.

Dennys shows you how to measure for the two different series of U Joints common to GM A bodies. You can have a hybrid shaft made if needed(different UJoint series on the pinion side to mate to that if it's different.

Denny's shafts are simply a work of art. I dropped the coin on an aluminum tube. It came ready to install, new slip yoke, U-Joints, balanced etc. A new steel tube shaft is affordable.