Technical Flathead Head Casting Numbers

I just brought home another Flathead engine with a 8R on the cylinder heads, can someone identify what this came out of. thanks.

 

My Green Book is buried under a mess of flathead parts...(neatly, no damage being done)

I seem to recall the '8R' designation to have been for Ford pickups ('49-'50) meaning 239 C.I. V8 engine. But:

Lots of the guys have the Green Book, expect an answer directly.

 

"8" means 1948 intro of the head, a slightly fuzzy concept because some 8 parts went into use in '48, others not until 1949 due to delays in new models.
R means truck version of the basic 239 Ford motor. Most engines have been rebuilt, messed with, or exchanged over the years, but whatever is under the head is likely some version of the '49-53 Ford engine. Differences generally are in things like cams and cylinder heads that are immediately discarded by rodders anyway.

 

I have had plenty of 8RT's but never an 8R, thanks for your response. tim