In someone else's truck that would be fine. In mine, no.
The big Cadillac was never offered with a manual transmission, so the crank has to be drilled for the bushing and there is no factory flywheel that fits.
There is an aftermarket flywheel available but it is spendy. A BOPC bellhousing will work, though I understand not all of them support the Cadillac starter.
So once you're that far you need a manual transmission that can deal with 500 foot pounds plus of torque. The New Venture and ZF transmissions don't seem to be real good choices and suddenly you have very few good options.
Aside from the fact I'm not a fan of manual transmissions getting one behind a Cadillac doesn't strike me as a project I want to take on.
