Two wheel drive S-10's are six lug, four wheel drive S-10's are five lug.
You can't use your existing rear end because it is a "closed" drive line. This means the rear axle and drive shaft are one piece. It cannot be altered to work. You still need a new rear axle and drive shaft that attaches at the transmission and at the rear axle. A closed drive line attaches at the transmission only.
On the T-5 trannys, you probably want a mid 80's to mid 90's. Probably the two best choices are the ones Schickling shows in his web site. The is a rather lengthy listing of the different kinds on the Inliners website:
http://www.inliners.org/ All of the T-5's in S-10 Blazers had numbers on their transmissions. They are "stickers" (white paper and green letters) and are on the top of the tranny.
Here's where I will ask someone else to give you some thoughts on identifying rear axles. I know that there are about eight different rear axle ratios, but other than pulling the cover and counting teeth, I'm not sure how to identify them. Maybe someone can teach us together. I do know it is a good fit for your truck. I also know that the right combination of transmission and rear axle is personal taste. I personally like the 1352.145 T-5 transmission with the 3.42:1 axle.
