Trans swap
The best way to accomplish this is to find another member who wants to go the other way and put both trucks side by side and start swaping parts. The trucks need to be compatable to make it a successful job. The same year is best, I don't know all the compatability parameters. But the closer the two trucks are the more likely to have few issues with the swap.
The big problem is that once you have a five speed, you have a host of issues just like a stock auto trans has. The five speed trans needs the mainshaft changed and the fifth gear, the syncros may be worn if it has serious miles, and of course you need a good clutch to hold what power you might decide to put through it. Sometimes the clutch upgrade requires a different input shaft too.
There really isn't much difference in price between doing a good full auto trans overhaul and upgrade and putting in an upgraded stick trans with a good clutch.
Just food for thought Greg L