quick questions 6.0 swap into 95 gmc 1ton 4x4

First off i wanted to say this is a great site. I was sent over from ls1 tech. I have a 95 sierra sclb 3500 4x4 i want to swap in the drive line from a wrecked 99 2500 4x4 silverado. Both trucks are autos and manual shift t-cases. Ive done alot of research but it seems everyone is keeping the original trans and t-case in 95 and later trucks. So im confused how to wire my speedo to the gauge and for cruise. Also how should i tackle the 4x4 wiring??? One last thing, i would like to use the 6.0 alternator is there a problem with this? It seems common practice to use the obs alternator is there a reason for this other than cost? I want to use as much from the ls truck as i can. I need a reliable work truck that uses of the shelf parts in case i have a break down away from home. I just wanted to say thanks alot again.

If anyone could help me with a topic or thread to search threw that would be great thanks.

your speed will work all you need to do is run the speed signal at tac signal with yo your cluster im not sure of the exact pins but i will get you that info. And yes you can use the 6.0 alternator, we do these conversions all the time

Thank you very much ray.
Chuck