just bought a 95 6.5 auto truck its a 1500 yeah thats right a 1500 it has tranny probs it shifts to 3rd and thats it, so in think with 289XXX miles it needs a rebuild. now what can be done to this tranny?? to handle some power?

If it is a 4L80-E and I suspect it is then all the power you can deliver to it from a 6.5 can definitely be handled.
There are a few reasons why it will not go into OD. Check the stickys. Read up on them. Check my prior posts and you will get an idea and how to ask the right questions. I wish you luck.