"whats more cost efficiant/reliable....puting on an aftermarket turbo kit or finding a turbo engine and doing a swap."
To fly economy class, find and purchase a turbo donor car. You'll need more than just an engine. Stuff like turbo manifold, o2 housing, turbo crossmember, ECU, injectors come to mind and will be far less expensive if you get them all at once in the form of a parts, or donor, car.

"Is it possable(easy) to drop a engine from a 91 into a 86 body (old style)"
Possible? Yes.. Easy? No... Very few have done this. It requires lots of engineering and fabrication. No kits. No instructions.

A guy with the screen name "Engloid" over at z31.com is attempting this project right now. He'll be the closest thing to a FAQ source, if he can get it off the ground. He's a seasoned mechanic and fabricator so there is a high probablility he'll make it work.