This came up on PGA Facebook this morning, and seeing as that will be lost to the world in a few hours, I figured it's probably worth starting a thread and making it findable information.
If you're looking to swap valve covers on a FWD motor, excluding the P12/T30 ones (anyone who knows about these feel free to add to this (Kieran?))
DE/DET Cover - Will fit VE and RR, but will need the black catch can on the front of the head
VE Cover - Will fit DE/DET and RR
RR Cover, JDM 1995-9/1998 and all NZDM - Will ONLY fit RR, cam oil squirters get in the way
RR Cover, JDM 9/1998-2000 - May fit anything, found on motors with no IACV on the plenum.
Last bit of info is courtesy of Shannon Johnson on PGA, who owns this:

A 2000 JDM RR motor, and found the cover fit fine on his DE. Note lack of IACV.
It's worth noting that the part number didn't change for the 1998-on rocker cover, so this is very much a test-fit-to-confirm deal. It may work, it may not, and it would be GREAT if anyone could back up Shannon's info.