The first thing I did to my '84 C10 was to remove the leaking TH350 and replace with a Muncie M20.
I am not concerned about doing truck things with this C10; only having fun.
The pedal box was a bit of a pain.
I found mine on the fabled online auction site and cost me $225.00 (my offer; listing price was $275.00)
You will need to pay attention to your braking system as apparently parts roe hydra boost differ from those with vacuum assist.
Installation was quite involved as well. Steering column needed to be removed and some bolts on the firewall were a real challenge.
It had been cleaned and painted and came with an almost complete manual linkage setup.
Only part missing, and a real pain to find was the frame mounted bracket for the bell cranl.
Go hydraulic to avoid this problem as well as header fitment.
All parts except the driveshaft bolted right in. the DS had to be shortened 3" and the speedo cable needed the stock 20" extension.
I also had to change the way too high 2.73 for a 3.73 posi.
Anyway, if you choose to move in that direction, good luck.