Hello,
I have a Progressive Peripherals Zeus 040 board I could sell:
https://bigbookofamigahardware.com/bboah/product.aspx?id=203 It is the 28MHz version. It's fully populated with 1Mx8 30-pin SIMMs, so 16MB is currently on-board. I currently have it set to auto-config 2MB of RAM, and the Init040 command is invoked to add the rest in the Startup-Sequence.
For CPU and heavy memory related functions, it's anywhere to 1.1x to 1.8x faster than an A4000 fitted with the standard A3640 board - according to AIBB.
The SCSI-II interface is reliable and the speed can be quite good. I have a Quantum ProDrive 1225S on there now and it gets ~2.6MB/sec. I had an older Quantum Fireball 52MB on there and it only reached ~800KB/sec - both measured with SysInfo 4.4. I do have a few other drives I could sell along with the board if desired.
This board works in both my rev. 6.2 (B2000CR) machine and a much older rev 4.2 machine as well. According to the manual I downloaded, it could be jumpered to work on an "A2000" or "B2000", but it doesn't break down which versions. I believe the A2000 it is referring to is the original German design, and the way they handled the CPU expansions were quite different.
I am located in Canada, so depending where you are shipping might get a bit pricey.
Send me a PM if interested.