Would I already need a 12 bolt w/ bolts ons, I kno it'll vary due to driving habits, maintainence and just some luck, but should I expect that I'll need one? Has anyone had experience w/ rebuilding and fabbing a boneyard 12 bolt?

 

If you avoid the high rpm clutch drops, your factory rear should live a decent life. As for finding a junkyard 12bolt off an older car, you have to figure that your car is a torque arm style suspension which the 12bolt rears of the past were not. It would be easier just to buy an aftermarket version to bolt right in.