I used to build them and on occasion rebuild them. I think they were all analog, but that doesn't matter. The problem is like you said, hard to find ISA motherboards and that has been the case for years. I happen to have an old working Analog PF in storage.

www.myrandomviews
"Old phone guys never die, they just get locked in some closet with an old phone system and forgotten about"

Retired, taking photographs and hoping to fly one of my many kites.