Vintage Air is another one, its well recommended. And not just for our rigs.
our issue is with headers, there is a lill interference w/the flange (header) & the motor mount or the body of the engine mounted component of the ac.
Continue ur research B4 the purchase to B forewarned of all issues. That leads to less surprises.
I believe the 4.1L U have would not suffer power loss, even on hills, etc. If in AZ/other hot climes - have the engine in top fit during the summer. If auto transmish make sure the radiator lines R clean. Should do fine! Didn't they come w/ac back in the day? Y not retrofit! They did have carb prts and other ac specific upgrades when engineered so ask around abt that. I'm uninformed...