Beater...Honestly It should still hit on 120 although that is weak.
but should be enough to fire and not worry about it.
Something else is going on.

If you want to chase compression you Can always put compressed air to it through the plug hole and listen for leaks. Breather/intake/exhaust air leak will give you a clue whats going on.

Bore scope might reveal something.

But it's usually the trans that is the weak point on those, and for a plow truck it's got to be solid.