Re: extractor gain?
I'm assuming it'll be using a vac sec carb or gas. I suggest Tri-Y not that 4-1's would hurt. 1 5/8" primaries is what they'll have until you got 4-1. Power gains depend on other things like head work, exhaust, camshaft, carb etc. Mine picked up 50rwkw when going Tri-Y->4-1's. Short shory is it was really strangled. Still is due to the triple flow mufflers I have.
XB Fairmont (street car) email@example.com.