273 mix matched head

I don't think there would be any "good" way to run those mismatched heads. Before I knew what I was doing, I inadvertently picked up a pair of 315 heads and installed them on my 67 273 Commando. The manifold did not seal — in 500 miles it had totally gunked the valves and blew oil smoke everywhere.

That intake is probably screwed. Where are you going to get a set of properly tapered washers? My rec is to start over with matched heads and intake. Odds are one of those heads is cracked, anyway. Last time I did a valve job they found both of my heads had cracks, and so did the first pair of replacements I found. It took six heads to find two good ones.