Lemmink is right, the only way is to add 32-bit memory via the 2630's RAM expansion connector. There's no way, other than possibly a major overhaul of several chips on the A2630, to remap the 2630 memory above the ZII address space. The good news is that the 2630 memory is 32-bit but as Dave Haynie explained, back in the day 8MB was considered a lot of memory and for compatibility with the original 68000 (fallback mode), placing the 4MB in the ZII space allowed use of the memory with the original cpu for compatibility. He made provision for extra 32-bit RAM via the access connector on the back of the card. But there is no simple way to change this arrangement.
On the other hand, Dave H has said would be possible to remap the 4MB of 32-bit memory space on the A2620 board, as the signal for doing so is apparently unused on the PAL chip involved. It would require a PAL replacement and a relatively simple modification using the aforementioned unused signal. Under this scenario you'd then have 8MB ZII memory available and 4MB of 32-bit memory on the A2620 above the ZII address space; so a total of 12MB. On the A2630, the unused address signal line was used for something else; probably has to do with the logic to make the A2630 asynchronous with the A2000 m/b.
