I looking to get a Demon carb for my GM crate motor. The one I'm looking at is the Crate demon for the 350 HO. It comes in vacuum or mechanical secondary. What are the advantages and disadvantages to these two types of secondary. The vehicle stays on the highway for the most part. I'm just wonering what would be the better setup. The vacuum carb is about $50 more than the mechanical. Is it worth the extra money. The setup is 350/700r4/np208/3.42, and it sits on 33,s Thanks for any ideas.