You found a Q-jet for the 350 from that other topic? Good, '77 is perfect. "Most" low compression motors like ported vacuum for the distributor. I would do that first, as Truracer suggested. If you end up with a crappy idle, you may need full manifold vacuum like I did on my '68 350 w/'74 heads. Ported vacuum nipple is "usually" the lower driver side of float bowl, but sometimes it's on pass side. A vacuum gauge will verify this. Everything else needs full manifold vacuum to work, EFE, THERMAC air cleaner, dash board controls, and EGR gets ported vacuum if you are going to use it. Power brake booster hose should have a threaded fitting on the rear of the throttle body, PCV goes to the big nipple on the front of throttle body. The big nipple on the float bowl goes to the charcoal canister, and the canister may use ported vacuum as a purge depending on your year.