How do I find an 8 3/4 rear in the jy
I have said it before, and I will say it again. This right here is shade tree bullshit. If you can weld, there's no reason for this. And if you can't weld, you shouldn't be doing this swap without going to someone that can.
Stock perch distance on an A-body is 43", center to center. Stock perch distance on any of the '65-70 B body rear axles is 44". That's offsetting a 2.5" wide spring by a 1/2" (20% !) if you do this redneck drilling operation, or putting a 1/2" worth of side load on the springs (which also decreases your tire clearance by a 1/2").
Can you do this? Sure, you can. But it will absolutely decrease the performance of your springs. If you don't notice that, well, you probably just don't know what a properly working spring is supposed to feel like. The other thing about this is that B-body and A-body perches are not welded at the same angle, so if you use the B-body perches your pinion angle will change, and it will likely not be correct (although there's more to this depending on how your car is set up for ride height).
The only right way to put a B-body 8 3/4 in an A-body is to move the perches. And if you're moving the perches, you can get a 1/2" spring offset kit from DoctorDiff, mount the perches at 42" c-c and GAIN an extra half inch of tire clearance, instead of losing a 1/2" and/or compromising the function of your springs. If none of this mattered, why would the factory make sure that the perches were the same width as the spring? You could save a bunch of money on production by making little skinny perches, or by welding all the perches in the same location (one tooling fixture instead of several) and just adding a big slotted hole for the spring bolt.
And this is the problem with the internet. You can always find someone that did something stupid and didn't die, so they assume it's ok. No, it's still stupid, it's still bad practice, and it's still bad advice.
I have said it before, and I will say it again. This right here is shade tree bullshit. If you can weld, there's no reason for this. And if you can't weld, you shouldn't be doing this swap without going to someone that can.
Stock perch distance on an A-body is 43", center to center. Stock perch distance on any of the '65-70 B body rear axles is 44". That's offsetting a 2.5" wide spring by a 1/2" (20% !) if you do this redneck drilling operation, or putting a 1/2" worth of side load on the springs (which also decreases your tire clearance by a 1/2").
Can you do this? Sure, you can. But it will absolutely decrease the performance of your springs. If you don't notice that, well, you probably just don't know what a properly working spring is supposed to feel like. The other thing about this is that B-body and A-body perches are not welded at the same angle, so if you use the B-body perches your pinion angle will change, and it will likely not be correct (although there's more to this depending on how your car is set up for ride height).
The only right way to put a B-body 8 3/4 in an A-body is to move the perches. And if you're moving the perches, you can get a 1/2" spring offset kit from DoctorDiff, mount the perches at 42" c-c and GAIN an extra half inch of tire clearance, instead of losing a 1/2" and/or compromising the function of your springs. If none of this mattered, why would the factory make sure that the perches were the same width as the spring? You could save a bunch of money on production by making little skinny perches, or by welding all the perches in the same location (one tooling fixture instead of several) and just adding a big slotted hole for the spring bolt.
And this is the problem with the internet. You can always find someone that did something stupid and didn't die, so they assume it's ok. No, it's still stupid, it's still bad practice, and it's still bad advice.
