[Barry_R]

Not sure where pop66ltd gets his info either. I guess we're even on that count.

There is no such thing as a high nickel FE block. Ford did not use nickel as an alloy agent in their casting process, choosing instead to use chromium and phosphorus. Any nickel that is in the mix would only be an insignificant trace amount, and only identifiable through spectroscopic analysis.

You may find 390 blocks with double webs, 428 blocks with single webs, and any combination you can envision including 390 blocks that say 66-427 on them. E-bay guys get all giddy about those. There was no religion to the use of the casting cores - this is high volume production stuff that was cycled in and out of service as maintenence and demand required.

Relying on external markings to select a non-427 FE block is a route to disappointment.
Living in and growing up in Detroit it is fairly easy to access a great deal of information. You ask the guys that designed and built them.

I've built one or two of these FE motors lately. They might be catching on....