Quick question- when I went thru the engine the gasket kit- Fel-pro came with 340/360 ports. Think I should use those again or 273/318 port sized gaskets. Kit was for a 1974 318 complete set.
IMHO, the mismatch between the intake ports and the small port 318 heads is way too big (just look at the 340 gaskets on the heads photo you posted). You'd be a lot better off with a small port intake to match your heads. THIS HAS NOTHING TO DO WITH YOUR VACUUM LEAK ISSUE. There are lots of small port manifolds around for a fraction of what the LD340 is worth. If you've got it all apart now's the time to fix this!
If you get the LD340 cut instead of your head then you will always have to have a shaved manifold to go on the engine and the LD340 will never seal properly on a correctly prepared engine (((so sad))).
