I did a 3" Ruf up front on a 1st gen and had a terrible pinion angle. I can see why 8" doesn't work at all. I'm not sure how the 5" lifts get past this. 1st gens just have a terribly short front d-line. The longer tranny and doubler went in at the same time and I have no more pinion angle issues. (I'm not sure if just one or the other is enough for your application..)
Depending on the wheeling you do, you can chew up your stock front hanger mounts quickly. (Rock crawling is hard on junk)