273 needs new heads, suggestions

While the thumb over the spark plug hole netted you little or no pressure, a leak down on that cylinder will tell you volumes more about the condition of the cylinder. The thumb test just gave you a place to start. Do a leak down on the whole motor; it might not be a head issue at all.

Eddy's will bolt down, and they come loaded with valves, etc. HOWEVER, you must notch the cylinders for valve clearance. If you went the Eddy head route, get the closed chamber, keep the chamber sorta on the small side, so you don't loose too much compression. Though you really need to know what pistons you have in the motor; hey it could be a Commando, God only knows and he ain't sayin.

If you went the Eddy route, and later did up a 360, the heads will swap over no problem, you can adjust your final compression with pistons, deck height and gaskets.

Good luck!