Rick,
it should work out ok for you. I have an old SD2000 that was modified by finders in Australia. I have 3 power supplies for it.
2-6 volt batteries with the domes on top, which duplicate the original power supply but without the extra headphone junction box. 2-12volt batteries and a Coiltek regulator that puts out 7.3 volts, that works great. Also 2-7.4 Li-ion batteries that velcro to the control box, for a light weight setup so I don't have to us the backpack for the batteries.
It seems that 7.3 or 7.4 volts is ideal for all the SD model Minelabs.
It's been said that the modified SD2000 with large mono coils really goes deep on the big nuggets. I wouldn't know since all I have around here is small stuff.
I think you will enjoy it.
Best of luck!
RSJ