Wow, Sounds like you're right where I was once. I have an 87 that I bought new as 2wd with 3.07s. I converted it to 4wd with an 88 mj front clip that had a dana 30 with 3.07s. Swapped easily. Then I ran up to 31 x 10.5 and it was a dog. I just installed 3.73 GS gears with solid single piece axles. It's like I have a different truck.
Just my input, I hope it helps.