['ol Pinion head]

A bolt-in axle version of the '73-77 8.5 A-body rear is your best bet for combination of strength along with having tapered bearing bolt-in axles. At one time I was pulling a few factory 3.23 ratio posi versions each year of the bolt-in axle '73-77 8.5 rears, so some used ones are still out there. A good 99% of this style used rear will only have 2.56's or 2.73's, stock, so don't expect easily finding a used low ratio'ed one in today's salvage yard searches. Have built up many as 3.42 & 3.73 posi's with new gears & rebuilt or new posi units, just gets to how much torque one is going to throw at one & how its torque loaded, to determine if such an 8.5 needs upgrade in axles & posi unit