The cheapest route would be to get a complete rearend from the junkyard...if you can
find one. However finding a junk yard rear that is in good enough shape to handle an
11-sec. motor will not be easy. An 8.5" ten bolt will be easiest to find. These are
found in '71 and '72 models. A 12-bolt Chevy would be your best bet. Either one will
probably set you back just as much as getting a carrier and gears for the rear you have.
A-body cars with posi rears in the junk yards are getting pretty rare. Another reason to
go with the Chevy is 'parts availability' and much cheaper prices. Olds parts very hard to
find now, so probably in the near future there will be even fewer.
Supercars Unlimited has type "O" ring/pinions
and carriers for 1967-1970 O-type
12-bolts. The carriers are
available in 2.56-5.00 series gear ratios, but are a bit pricey: right at
$500.
Richmond Gear has 3.42, 3.90
and 4.10 gears, but are made to mount on the
2.93-3.23
carrier, not the 3.42+ carrier as the original Olds 3.91 gears mounted on. Richmond
decided to make them this way because most people looking for
aftermarket gears have a 2.93-3.23
carrier...and because it allows them to make the ring gear thicker/stronger.
Reider Racing sells a special-made posi unit to fit the 12-bolt Oldsmobile rearend. It
seems this posi is a modified unit from a Mustang that is machined to make it fit the Olds
rearend. The Reider tech rep does admit, however, that it was 'probably' not a good idea
to run this unit with a strong 455. His quote was: 'After all - this posi is one of the
first things a serious Mustang racer would replace and it is not really designed to handle
the amount of torque the Olds would produce.'
The best route for long term reliability for a hot street and strip car is a 9-inch
Ford rear from one of the big rear end guys: Currie
Enterprises, Tom's, Reider Racing, etc. They can build
you a bulletproof rear end that will bolt in to your Olds.....The price is in the $2K
range........
BTW, the Olds rear is worth at least $5-600, if you can find them.
