‘65-‘70 covers two different widths for the B-body 8 3/4 rear axles. ‘65-‘67’s are 59.5” wide drum-to-drum and ‘68-‘70 are 60 1/8”. So if you want your tires to actually fit those axles would use a different wheel backspacing for maximum tire width.
I suppose if you’re jacked up with SS springs or higher in the back and hang the tires outside the quarters it doesn’t matter.
Welding new perches on isn’t hard. You already have the rear axle out of the car, so, even if you can’t weld it’s easy enough to get it done. A-body and B-body 8 3/4’s also use different pinion angles, so, depending on your ride height the B-body stock perches will likely need pinion angle correction. No welder? Set the axle on the perches, loosely attach the U-bolts, rotate the housing until the pinion angle is right, mark the perches, and off the the welder. Piece of cake.
And here’s the real deal, if you’re moving the perches already it’s a great time to install a 1/2” spring offset. I mean, that’s a win-win. You get an 8 3/4, you pick up an extra 1/2” of tire clearance, you set the pinion angle for your car and your ride height, and your springs react faster because there’s no side load. That’s even good for drag racers!
I mean seriously, does this look right? Think about how the spring is gonna sit with the pin in that left hole.
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Will it wreck your car? Probably not. But it sure as heck isn’t right. Little things like this add up, bad suspension geometry changes how your car will handle and launch.
