Here is a scan of the RAM cart and both extension carts:
http://home.t-online.de/home/chrisnowak/ramboard.jpg
One extension cart is used for an 8bit data bus (SNES) and the other for a 16bit data bus (Genesis).
Schematic of the RAM cart:
http://home.t-online.de/home/chrisnowak/ramcart.gif
And of the 16bit extension cart:
http://home.t-online.de/home/chrisnowak/16bit-extension.gif
This is actually everything you need for the Genesis, you just need to know how to connect it. I'll either write a textfile or make another schematic...
/chn