mamba max pro and mamba 2650 in 4s?

i just bought a rc8t and i am about to install the conversion kit in it.

i already have the mamba max pro and a bunch of 2s lipo and i would like to run 2 of them (i have 6 pairs of the same brand and mah)
so i was wondering if running in 4s with the 2650kv motor would be a good option?

i am planning to convert my rc8t in a sc8 later.. (much smaller wheels)

let me know if i'm on the right track and what pinion size i should start with!

Thanks for your help guys!!