Yes, the analog boards from a 128K, 512K, 512Ke and Plus are interchangeable.
The 128K motherboard can easily be put into the MacPlus chassis. You may need to check the +5volt rail adjustment when you swap boards.
Test initially with floppy drive (emulator), mouse and keyboard disconnected to minimize other causes.
I ideally want to keep the 128k original chassis and put the plus analog board in, being extra careful obviously.
the board might need a refurbishment anyway.
The emulator is not mine, it’s the guy who had the Mac who has it but he is 2 hours away from Sydney where I live.
I really hope I can get it back to a good shape and keep it.
do the analog boards have a serial number? I would love to have it like an original not a messed up Mac.