Your clutch diameter is dependent on your flywheel diameter. A 168 tooth flywheel will take a larger diameter clutch than a 153 tooth flywheel. Which do you have in the truck now?
Also, if your switch flywheels, you will have to change out starters (or the starter nose) to correctly engage the flywheel. Some starters have a dual pattern.
This might help.
https://www.chevytalk.org/fusionbb/s...hp?tid/171683/