So, I'm in the middle of literally doing a 3/4 drive train swap on my barracuda. the wheels are being replaced, the rear end (7.25) is being replaced with a 489 8.75, and the engine is being rebuilt. Literally the only thing staying the same is the transmission. So I"m sticking a 489 housing out of a 68 Charger in the rear end to replace the 7.25 and I have a few questions.
1. how far do I need to narrow it. new wheels are 17x8 with a 4.75 back spacing.
As far as narrowing, I would suggest securing the car on stands, place the wheels/tires in the wheel wells where you want them and measure the distance between the two wheels where they mount.
2. is the body being off 3/4 of an inch normal. like one side with 245/60 15s in back clears by that much and the other drags?
The drivetrain is usually set to the right of the vehicle slightly to compensate for the engine being set to the right due to steering clearances.
3. what do I need to set the new pinion angle at?
I replaced my 7 1/4 in my 74 Sport with an early B rear, I maintained the same pinion angle.
4. What is that castlated nut on one axle? Does that set the bearing preload or something?
It is for setting axle end play.
5. Can I use sealed outer bearings on it?
If you're referring to green bearings, then yes. If it's a suregrip you may have to remove the thrust buttons or block from the center section depending on which unit you have.
I'm trying to get this all done asap so if someone could help me soon I would greatly appreciate it.