Not for nothing but I always thought that the rear tread width increased by 1 inch in the '68 model year. but checking Zazarine/Roberts "Pontiac Restoration Guide '64-70" '85 edition states that "the rear axle design was unchanged for 66-67 although the '67 rear tread was widened one inch". pg. 307. Yet several rear end catalogs indicate as I suspected and as was stated the axle width change occured between 67 and 68.
While Zazarine/Roberts book identifies several and various changes in the 66-70 rear end designs such as spring perch changes, tread width changes differential information stamp locations, new ring gear, bolts and differential case changes and the intro of pontiacs 12 bolt rear plus two types of axle bearings available in '70 10 bolt rears. no mention is made of upper control arm mounting location changes. That does not mean it didn't happen. And this aint the bible but with so much info on other changes.....?
If that does not confuse you enough.... Parts catalogs indicate that although lower trailing arms are the same between 64-72, uppers are different between 64-67 and 68-72. Further more the rear crossmember reinforcing braces available on manual trans models was also different between 64-67 and 68-72. But the no-hop/ anti hop bars manufactured by Edelbrock and others designed to decrease pinion angle, mounted to the upper control arm mounting points on A-body rears fit all A-bodies 64-72. so I think the difference is it the frame, not the rear upper control arm mounts on the housing.
I think the upper trailing arm mounts are all in the same location on each rear but pinion angle will change if you accidently use the wrong year upper control arms. Stick with the ones that go with your frame.
i'm just as confused now as you were befor reading this. Go deep into left field and buy a moser rear and all new arms from Hotchkis, what the hey! Kids diapers dont fill up if you stop buying them food and if you put peanut butter in thier mouth they stop cryin too. Its win win all around! Unless wifey wises up to it and sneaks off to buy shoes or a hand bag.
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