[DanEC]

I'm going by Colin Comer's recent book that says early 427 cars were low riser center oilers. They would still be cross-bolted blocks. I think cross-bolting began sometime in the era of the 406 version.

This makes sense because the 64 Galaxie's with 427s were still low-rise, center oilers. I believe they carried over sometime into early 1965 model year, which I think (?) is when the side oiler and medium riser heads began to appear. Correct me if I'm wrong.

In reflection - it may have been when the 427 LR first appeared that cross-bolting first showed up. I'm not sure 406 mains were cross-bolted.