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The ports were defined over the years from track experience and testing on a flow bench. Dad has a rubber casting some place of the final port configuration someplace in the parts bin. A marine type epoxy was used on one side of the port to help change the flow path, but that would not explain the epoxy you have on the outside. Perhaps it was used to repair a leaking push rod tube.
Keep in mind after the bikes were sold many were used for years after so its hard to tell who did what to them.
As for the heads in the pic, its impossible to give a specific history. I will check with dad but i thought those bikes had smaller plugs on the lower side. They do appear to have the airflow insert on the intake port, some close up pics there might help. Are the valve guides modified? They could have been replaced, but some of the heads had them shortened to reduce the material in the port.
Oddly, when BMW wrote the check to buy the parts they were supposed to get everything. So these heads and the transmission must have not been spread out on the hanger floor in Texas when i was out there to inspect a few years back. If they were there is a good chance they would have been on the bike today. Oh well all history at this point.
None of the bikes he built use 14mm plugs on bottom. They all had 12mm.
He noted immediately these were R90s heads. When I questioned the year he noted that R90s was available in Europe a year before US. So these would be first year production.
Another observation is that some weld was usually added below the push rod tube to add a bit of strength were it was opened up.