71 Dodge Charger 400x6. The previous owner was going to put it on the drag strip back in the late 90's so he put a 4.10 Sure Grip in it, then put it in a warehouse where it sat for many years. I obtained it about 4 years ago. Everything is perfect now except for the 4.10, it has to go. I am going to put a 3.23 set in it by just pulling the existing case and plugging in a different one.
I haven't done this before, so I have some questions. The housing has a large '6' on the side, so does this make it a 489 or a 742, or is it something else? Are the different cases interchangeable? There are a few places where I can order a complete differential, but I have to get it right so the thing fits.
Large yoke? What are the options and how do I tell what I have now?
Spline count? I'm pretty sure these are the splines at the end of the axle that insert into the diff, how do I tell what my axles are other than pulling one and counting?
Dumb questions probably, but I want to make sure what I end up ordering actually fits and works.