Hmmm- so there shouldn't be any way to switch from one to the other?
That's good! Since this had a 2-pc (rightly or wrongly, we dunno) to start with, and it
looks like the 2-pc fits "correctly", I'm gonna say this must be a considerably older block than I thought... (it's not handy or I'd dbl-chk it).
Cool!
Thanks for the replies, sorry if wasn't communicating my confusion earlier. Mainly I was unsure if the seal *groove* was different,
i.e. was the 1-pc just an improvement and you could use either one, or if the groove IS different then you must use whichever it's designed for...
Russ R