Technically there isn't really a 4000 version. It's just a relabeled HC8+ Rev II with software enhancements to get around the DMA problems these cards (and A2091's) have in the A4000. Hardwarewise the cards are identical.
2 4MB Simms will work guaranteed on the Rev II models (A2000-HC8+ Rev II, A4008, A4000-HC8+ Rev II) and the even have the jumper settings (4MBx1) silkscreened next to SIMM sockets and jumpers.
It's very likely that the Rev4 and Rev5 board (with the larger SCSI chip) will also work, but this has not been confirmed.
The older Impact 8+ likely will not work, this is the card with 8 SIMM sockets but is a fully populated board; ie no room for a hard drive.
