The problem with using the '68-up 340 exhaust manifolds on a '66 and older A-body 273/318 is that they don't fit the body very well, you need to custom make the whole exhaust system, and you'll have a hard time keeping head to manifold gaskets from blowing out due to the very thin sealing area on the mismatched port sizes between what a 340 head has for a port, and what the 273/318 head has.
I thought we were talking about 67' 273 heads. I have hanging onto a 65' 273 4 Bbl intake being it's rare and compatible for the early 273's. I tossed the 65' heads out last year due to its small ports. I can't keep everything.
