well, i have access to either a 4th gen rear, or a 9 bolt rear, and i'm trying to decide which one to go with, if I use the 9 bolt it needs new calipers and disks (could I use the 4th gen ones?) and if I go 4th gen I need new rims and axle shafts. what do you guys think?

the aussie 9bolt is a better choice!
it is stronger than a 10 bolt,been through the debate 100 x's the only true drawback is the available gears for the 9 bolt 2.77,3.27,3.45 easy to get now 3.70 and 4.10 will take some hunting TPIS has the 3.70 but its like 400.00.
if you are ok with the avail. gear options you are good to go.

I have the 9 bolt and love it. However I've been told that the calipers are expensive because of the parking brakes in them.

seeing as i already have this thread, how do i know which gear it is. the rear may be original to the car, but it looks like the doors and center console arent.

9 bolt is stronger, but if its too worn out, i think i'd go 4th gen. however i hear eaton is gonna make a 9 bolt posi, so then again...