Smoke from breathers.

Very cool Valiant! :D. I think the easiest thing would be to do a compression test first and look for inconsistancies in the individual cylinders. That may rule out a head gasket failure. Low consistant readings would lead to lack of ring seal. It's a little hard to tell what a low reading would be not knowing the piston used, the deck ht, and if the heads were milled. If all those measurements lean toward the stock side, that's a very low compression engine in that configuration. The fact that you pull 15" of vac say the cam is fairly mild. If it is a Eddy cam i would guess it's the regular Performer?