i ran my 4kw off a single yellow top up front with 1 pos and 1 neg runs back to the amp. and 6 runs of 1/0 between the 220amp alt and that yellow top. withthe rmp's up i managed to maintain 12v and the amp never heated up even after daily bumping.
with that alty and extra bats you'll be fine. i highly recommend at the very least a dedicated neg run of 1/0 for every pos run. dont bother with chasis grounding when you're pushing this kind of amperage. to be nice to your electrical dont bump when your rpm's are low.
and if you took a SS 6500d over a mojo 4kw you should be lynched, this mojo is a FAR superior amp. one of the best 4kw range amps IMO