['ol Pinion head]

Originally Posted by corn goat

what is a bop 12 bolt with 390 gear worth?other than what some one would pay.

To answer your question, need more info.

-Is the rear a '67. 68, 69, or '70 Type "O" Olds 10 bolt that is assembled with 3.91's?
-Or is it some sort of c-clip 12 bolt rear with a 3R u-joint flange?
-If a type "O", what year and ID code on the housing?
-Is the housing a clean & unpitted housing or a deeply rust pitted mess? Are the gears GM, or Richmond?
-Typically, '70 type "O" rears will still have good axles, as they are tapered axle bearing design, so seldom a reason to replace if stock powertrain.
- On the other hand, the '68 factory assembled 3.42 & 3.91 Anti-Spin typically will most likely need new axles....chewed up under the sealed axle bearings. Ordering a pair of new Mosers, & installing new axle bearings, studs, & inner seals will run an easy $425.

All the above will effect value.
Sold a totally restored '69 3.91 Anti-Spin earlier this summer. Very clean housing with reman posi & very nice original gears. Have a '68 3.91 Anti-Spin setting in the racks. It will need axles.