This will solve the ram problem with A3640s.
X-Calibur. If you can find one. Major modification of the floppy/powersupply sled is needed for desk top use. This card sets on top of the A3640 and the ram is vertical. Intended for A3k/4k tower systems. There are other modifications needed such as cutting, soldering and crystal replacement.
With A3640s failing at a steady rate due to the capacitor snafu, a WarpEngine is the better route as it has SCSI II interface and it's pretty much plug and play. Even then, the floppy/powersupply sled needs some drilling for the fan and heatsink to breath. Also, only one HD installed helps keep the heat down by having some air space inside the case.
laterz