After going back and forth between Lithium and Lead countless times, I've finally decided on Lithium! LiFePO4 to be exact. These are a relatively new battery chemistry that don't have the energy density of other Lithium Ion batteries, but they are significantly cheaper and much safer.
They'll last 2000-3000 cycles depending on amount of discharge. I've ordered 30 cells, 3.2 nominal @ 100AHr, for a 96V nominal total voltage. Minimum voltage for a cell is 2.6V, which corresponds well with my controller's 80V minimum. Maximum voltage for a cell is 4.2V, which at 126V peak won't overload my motor. The batteries should fit in a single grouping underneath the hood, and the final weight/balance of the car will match very closely to stock. I purchased with a group from diyelectriccar.com - batteries should arrive in 2-3 months.