Timing chain

But… but… but… I could have sworn I saw flanges on this 6-banger? I assumed they were holding the three heads on.

Yes, the 6 cylinder had removable heads. It was quite common for engines in the early days to use use either individual heads for each cylinder or paired heads, as many as necessary for each bank. There was no problem keeping the heads in alignment because the rpms and specific output were low.
I only referred to the 4 cylinder “Offy” or Meyer -Drake because that is the engine people are familiar with in everything from Midgets ,Sprint Cars and Indy Cars from the 30s through the 60s.
That engine came in sizes from 90 cubic inches in Midgets to 270 in Indy Cars and those are the engines that had no removable heads.