I bought the one with the - bus. I actually was able to move some OEM harness just enough to mount it on the firewall (in the engine compartment, battery side) Also mounted one of Blesea's single maxi fuseblock's ahead of the distribution fuseblock. I think in one of your posts elsewhere you mentioned a breaker in this position.
To mount the dist. fuseblock I needed to fab a standoff bracket for it.
PITA. Little room for this stuff on our trucks.