It's a lot less costly then trying to change from an auto to a manual.
Depending on whether you already have the tranny or not, it's cost will have to be considered. If the truck is a SBC, them there are several transmissions that will interchange. The t350, t400, 200metric which has overdrive, and a 2 spd power-glide.
The clutch pedal assembly will need to be removed and all the linkage.
The transmission, clutch, pressure plate, shifter, pilot bearing, and flywheel will also need to be removed.
You will need the trans., torque converter, flywheel, different front drive-shaft yoke, and possibly the starter and cross-member will need to be replaced.
It is easier to add a floor shifter for your auto then to try and change out the steering column and run new linkage.
Price wise, your looking at around 500 for labor and at least 1000 for parts. Depending on where you are located the labor could double and depending on whether you want brand new parts or used parts, the price could reach 1500.
This is a time consuming job, but not an impossible one.
Hope this helps. Christopher