Chiphead,
The correct 8.5 A-body rear is a direct bolt-in in your '67, & is easily built stronger than a typical $1200 12 bolt Chevy rear. To make a 12 bolt posi rear stronger, it will require aftermarket side gears & spiders, & typically, aftermarket axles. Weak stock spider gears & often weak c-clip axles are the bane of the often hyped 12bolt.
Back to the 8.5... To fit such an 8.5 A-body rear, your factory 8.2 driveshaft will need to be shortened 1". 54.25" wide??? might check your 8.2 r/e for its casting date, & see if it is a '64-mid 66 piece. 8.2 r/e's often got swapped over the years, as most would not hold up. Having blown up more than my share of all versions of 8.2's & 12bolts, many moons ago I stumbled on the 8.5 A-body rear as the vesatile r/e to build.
Narrow vs wide... its only a 1/2 inch on each side. For most, the 1" wider A-body rears will fit easily. One can get in a jamb, however, if running rear wheels with MAJOR positive offset. Over the years of doing 8.5 A-body builds/swaps, managed to even fit an 8.5 A-body rear with 275/60/R15's on 15x8.5's under a '64 Chevelle... no A-body rear wheel houses are tighter than the '64-65 Chevelles.
For comparison, following r/e's are 54.25" backing plate to backing plate:
-'64-67 Chevelle 8.2 10bolt (c-clip junkers)
-'65-67 Chevelle 12 bolt
-'64 (small upper control arm bushings) BOP 8.2 A-body
'65-mid '66 8.2 BOP
55.25" backing plate to backing plate:
-'68-70 Buick 8.2 10bolt
-'68-72 Chevelle 8.2 10bolt (c-clip junker)
-'68-72 Chevelle 12bolt
- mid '66-69 Pontiac 8.2's (sealed bearing axles)
-'7O-72 Pontiac 8.2's (tapered axle bearings)
-'68-70 Type "O" Olds 10 bolt yes it has a 12 bolt cover, but it is a 10 bolt!
- Early 8.5 A-body (all 3 housings/tube versions)... all had bolt-in tapered bearing axle retention.
56.00+" backing plate to backing plate
(upper control arm mounts are cast too wide to use in earlier A-bodys)
-'73-77 8.5 A-body (c-clip axles)
-'73-77 8.5 A-body A-9 bearing bolt-in axles
-'74-77 8.875 M-P series A-body rear (c-clip)
-'77+ B series 7.5, 8.5, & 8.875
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Buzzards gotta eat... same as worms.
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