More of a wild guess than an estimation, but I mean doing the work yourself I guess. <img src="/forums/images/graemlins/notooth.gif" alt="" /> Sorry dude, there's just too many variables.
I notice NO information about what you have now other than a 4 cyl Jeep unless the 1994 part of your handle is a clue. If you have a 1994 2.5 that won't go over 50 with 32" tires it must be tottaly worn out or else it has other serious problems. My buddy next door has an old (85) CJ with a seriously worn 2.5, Stock gears and 32" tires and he has no problem maintaining 60. If it's freeway speeds you want put some stock size Tires (225 R15?) on that thing and get a tune up.
I bought a good running 4.0 yj complete for 1500. A feller on another thread picked one up for 900. I could swap all the stuff I need for the conversion into my CJ for very little cost by doing the work myself and then selling the left over YJ parts. But I'm not in college! I have time and tools. But wouldn't it make more sense to sell the CJ and fix up the YJ for off road? Enough of my dilemmas, but you can see sunders point I hope.
Your question is just one of those that has no simple answer that you want to hear, I suspect. Don't hold back, feel free to tell us more about what you have now and I'm sure folks on this board will be happy to try and help you get it running better. <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> Whatever you decide, Good luck!