You will have 5 lug front and 6 lug rear then. What do you need to upgrade? gearing? strength? width?
What are you trying to get out of it? The 7.5" isn't as weak as it's made out to be. Unless you are running really sticky tires and putting down at least a few hundred WHP, you'll not have any issues with it. Disk brakes are easy enough to swap on, and LSD's aren't that expensive if you do some research. The Explorer axle is about the same track width and can be had with an LSD and disks for (I've heard) $200ish. You'll have to also have the driveshaft modified though.