['ol Pinion head]

La Cabra,

Understand where you are coming from axle spline wise, there were many different versions of bolt-in 28 spline axles used from '64-72. Today, many folks just assume, in a search, that a GM muscle era axle had a certain kind of seal, 28 splines, & a certain length, then it will fit their application. Problem with this suppositition is GM Divisions all had their own axle (Differential) divisions, & up until late 1970 each had a lot of autonomy. Just one reason I stock a wide variety of used '64-72 axles & try & ID them all before putting them in the racks.

ID'ing your rear... Considering your original rear has an axle seal outboard on the axle, & has 3 holes in the axle flange, I would look the rear over closer, does it have U-bolts retaining the u-joint or straps with 7/16" headed bolts. The straps & 7/16" headed bolts are a tipoff for a 8.5 A-body rear... a very popular upgrade. Problem with jumping to the conclusion that your rear is an 8.5, is the 4 pinion cone carrier, the first 8.5 posi carriers (Warner-Motives), while cone style, were not 4 pinion but 2-pinion units.

All things considered,
-4 pinion carrier,
-3.42 gearing,
-external axles seals,
-& the kicker... 3 access axle hole acess flange. Am betting the 8.2 10 bolt rear you have is a '70 model Buick Skylark-GS piece. Basically a process of elimination as Pontiac A-body bolt-in axles always have one access hole in the axle flange, while Buick & Olds had 3 or 4 access holes & external axle seals & tapered axle bearings did not show up till the '70 model GM rears. Further, in sourcing a staight used axle, some care is going to have to be taken, as the most common "3 hole 28 spline external seal" axle is the "8.5 A-body" axle. This axle's 28 spline end is slightly different & will not slide in a 8.2 Pontiac 4 pinion carrier. Considering a '70-72 8.2 GTO axle will fit in the '68-70 Buick 4 pinion carrier, I seriously doubt the more common 8.5 A-body axle will fit in a '68-70 Buick 8.2 carrier, as such, one is going to need the '70 Skylark 8.2 10 bolt axle.

Hope this has not been too confusing, will try & ck in late tonight.