I don't remember a #61 head but there have been lots of different castings.
As long as it's an Animal head and has not had something illegal done ,like port modification, it should be fine.
It is not legal for a LO 206.
I saw one and a while back. Definitely an older casting around gen 1 or 2 likely. Not a very good port and didn't flow well. Much better off with an rt1
For an unrestricted engine, go with the RT-1 head for sure.
Now, on a small plate engine, I've seen some very small gains with particularly smaller IN runner casting heads.
Is it worth all the sorting? Probably not. It does make a reasonable way to use up the older casting heads though.