33 is normal in a no AC vehicle.

No VSS is probably most of your problem, and too cold a thermostat is the rest of it. VSS tell the computer if the truck is moving and how fast. Without it the computer has no idea and you start to see stumbles and stalls, especially when stopped.

with 37 there I almost think it's a wiring issue and both VSS and TC codes are present. I seem to have a vague recollection about wires getting corroded back behind the battery causing issues.

VSS screws into the trans at the speedometer cable connection
https://tinyurl.com/y7omwhne