Can I replace a 94 dodge ram 1500 3 Speed Transmission with the overdrive one so 4 speed?

My work van started leaking trans. fluid pretty bad on the way home from work coming
from the dust cover area so I knew it would have to come out and I know a pretty good
guy to remove and replace them. He got it out but we cant tell were it was leaking from.
torque converter shaft looks little scratched up the seal looked really good around it but
we pulled it out and the brass bushing around were TC goes looks very worn to were
half the brass has worn off . And there are metal shavings in the fluid as well as the
fluid is black due to proper maintenance. So what Im asking is sense i am unsure were
the leak is and i need new TC and pan kit at lease and try that or buy a rebuilt 4 speed
i found with ne TC for $300.00 with is a really good deal.