I would definately get the aluminum heads. I assume you are running an open chamber head now? Maybe a 906 or something. If you are, you could get the 88 or 84 cc eddies and if compression is a concern, shave a couple thousandths off to get that combustion chamber down to size. If you go with the Indy EZ, I think they come standard with 78 or 74 cc combustion chambers. Remember, both heads are good, but the EZ's have more potential in them than the Eddies....for future builds.
It sure would be nice to know how far (if at all) the piston is down in the hole of that motor. If it's a 451, somebody had to build it, and it would be kinda weird if it wasn't zero decked....
EDIT: now that I have re-read your post about 3 times, you're going to pull the heads off anyways, right? Might as well do a little measuring to see what's going on in that motor while you've got them off....and after that, you can make a better informed decision. If it were mine, I'd buy the aluminum heads, but not everyone out there is a horsepower junkie like I am...