dump the wimpy 70 amp and go for 120 amp bosch or valeo (you might need to keep your pulley though). The 120amp is cheaper (go figure). If you really wanna overkill go for 143 amp or 150 amp
You will also need the wiring harness.
I think 143 amp is on 98-99 models. Theres a great thread on here (I think from GSXR, I will try to find it).
Or you can call call at The Benz Store in Atlanta, he will set you up with all you need. The 120 amp he sold me fit fine, no need to swap pulleys and its running perfect.
You want 14-14.5v at idle and w/all acces on. Any less will less/more reduce battery life.