Have a word with Sprink on rcmf he converted a 68" Yak
Think he went with an AXI & also dont forget Plett motors either have heard good things about them.
I would say that be a little careful about making the battery capacity choice. Make it after the motor etc are in as any nose weight can be extra capacity.
But start with looking at setups giving over 1500 Watts and you will be ok
If you need a hand with figures ill run it all through Motocalc if you want to give a rough guide just PM me on 3DRC.
Am running myself in a comp arf 2X2 12.5 lb a Hacker C50 15xl with Evo20 10s 5000mah gives about 2500 watts on a 22X12 apc "E" as a guide for you.