. . . . . . pretty sure it was a non drilled block among other things that made it unique.
I'll start with: "I don't know"! That is, if in fact the blocks were uniquely un-drilled or not.
But if you consider the efforts generally put forth to reduce costing in production, and that particularly considering the issues of limited product runs, if only in the attempt to justify such, then consider the fact that by eliminating the drillings, this just skipping a process (which was an already known execution, and since seemingly required more than one additional set-up in the machining process so perhaps better said a "couple of processes), would have been a beneficial cost savings! Whereas, the effort involved of producing a new product ("plug kit") for such would prove as an added expense (consider, even after engineering, how many departments would have had to "sign-off" on this!

), which would have made better business sense?

Scott.