Rear axle geometry???

Hi all! I have recently bought a dana 60-2 (narrowed) to replace the AMC 20 in my 82 CJ7 on 37's. I bought the jeep with the 37's but the PO decided to not worry about the stock 2:73's. Not to mention it has a T5. The dana 60 was originally set up for a spring over but I have new perches to bring it back to spring under. What are things to consider as I'm mocking up the new perches to weld on?? Geometry of drive shaft? Anything else I'm missing? I know how important front drivel shaft geometry (which I need to tackle next) just not sure about rear. Any help or suggestions are appreciated.