i want to make my truck 4wd any tips where to get front ends and transfer case and any experiance opions on how difficult it will be??

This truck is so old it is probably cheapest to buy a whole donor truck with a bad engine or wrecked or rusty body. Look at the frame of the donor and your truck, see if the holes are drilled on your truck and the frame is the same. If not, swap the body and engine from your truck to the donor. You'll need a pretty good hoist frame and slings to hoist your whole body off, and some way to push the frames around while the body is in the air. Use stacks of railroad tie or landscape timber (6x6) pieces (2' long) to protect yourself against slippage while you are under it. Hint- chainsaws cannot cut a tarred tie, use a sawzall. If the frame holes are predrilled and the frames are the same, you can think about just swapping axles, brackets, and transmission/transfer. If you do that, measure and match diagonals (front left -right rear etc) to make sure your truck runs square when done.

If you are serious about making the conversion, it can be done. I inherited a 1990 Extended Cab F250 2WD from my father and I too wanted a 4WD. With a lot of sweat, help from two friends, two junk yards, one trans shop and the web it came together. My life saver was my father-in-laws 90 F250 extended Cab 4X4 to get the correct hole positions when changing from springs to leafs. I am now a proud owner of an older 4X4 that only had approx 60k miles on it. It did cost me more than if I had just bought a used factory 4X4 that was already setup the way I wanted. But I think my father would be proud of how it came out.
The hardest thing at the beginning is finding the closest matched truck “Cheap” to what you have. I finally picked up a 1992 single cab at a lean sale from a tow yard.
I used my trans, changing the tail shaft and case. Went ahead and put in all the correction kits for my E4OD trans. The transfer case also needed a shaft and tail housing change due to the difference of an electronic speedometer. I did find that the dash and wire loom was set up for 4X4, just had to change plug configuration and add bulbs. Shortened my drive shaft, lengthened the front drive shaft. Installed new Leif springs that had a 2” lift to level the truck.
Don’t want to do it again, but I’m glad I did it once.