You may notice that the donors are all "granny cars". Many will have low miles. My head was loose, but barely needed a valve job, and had guides within spec. Granted, we did a whole lot more to it, after that, that you will not need to do. I did a bunch of the machine work, and my machinist did the rest. Even if you are paying hourly rate (or flat rate), getting the head in good working order (don't forget to mill the deck!) won't set you back too far. I cannot emphasize milling the head enough. Early engines had dished pistons, and small combustion chambers. Late engines had flat-top pistons, and large combustion chambers. Mix without milling and you have dished pistons, and and large chambers. Fine for a turbo, or blower, but not so good for natural aspiration, unless the plan is to run 68-octane.