[othello]

If you flip your centerdiff by 180° your motor could be placed on the opposite side of your steering servo (front left). This way you would most likely have enough space to place 2 4s1p A123 packs in sidebyside config behind the center diff (giving you a well balanced buggy). With 4s2p A123 a 2200kv motor will rev up to 24000-26000rpm under load. With a somewhat bigger pinion you should be able to gear it for 40mph. A123 cells in 1p config are able of up to 100A but voltage can drop to 2.3V at this load. This gives you 230W peak per cell. With 8 A123 cells you will have around 2000W at your finger tip. Your limitation will be the Mamba max ESC which most likely is able of short peaks around 100-130A: up to 1400Watt (more then enough for a buggy).

Depending on the height of your body you might be able to fit 5s2p (humpback config 3+2 or 4+1) which would give you around 31000rpm under load.