I put it into gear and it dies.

The PCV.
It adds about 3 cfm at idle. An average size V8 with a stock cam draws about 17-21 cfm at idle.
The carb, if designed to use PCV, will have it's passage sizes & any factory bypass air [ fixed/drilled passage ] sized to work with the 3 cfm from the PCV to have the correct T-slot position at idle. If you eliminate the PCV, the extra air has to come from somewhere else: usually cracking the t/blades open more....which will now mess up the delicate T-slot position. There is no reason to eliminate PCV, it is a really good system that has worked well from day one...