If you already have a lot of money in the truck, I assume it was done to correct other deficiencies, yes? If so, then you have one more to take care of...the transmission.
I had a '99 and it needed some work and it needed more power than the 318 would ever be capable of. By the time I added up all that I wanted/needed to do to make it into what I wanted, I was looking at a LOT more money than it was worth. Not a good financial decision.
So, I went for a newer truck. I'm very happy that I did because if I hadn't, I'd still be working on the '99 and not enjoying a HEMI.