Been getting help from Kelly (thanks buddy!), but hate to bombard him further. My ac/45 'd' block seems totally as issued, except for the gas cylinder (?) which is the early blued version. Found this one in an old thread on another site and want to approach the guy about a trade, but obviously want to make sure this is the one I need, as I think my most likely source will be a trade from a shooter with the late cylinder. Pic below.