Scale Tank rebuild, what motors to use?

Hey Brian, I have some figures. The Transfer box gives 16-1, but I still would like to loose it, as its so heavy.
The circumferce of the Sprocket is 361.1mm As for the Voltage I was kinda hoping that 24v would be enough, what do you think?
I am still wondering about the chain drive raitio, Is it a case of getting the biggest redution in the space available?