@Les1 as you know there is no room under step. I was able to get my 300a fuse and battery monitor shunt down there.
I placed 2 runners front to back to get inverter above hoses and created a chase for ac and dc wiring. I ran runners side to side to mount inverter to over the trough.I removed sink drains so they could be rerouted later. I installed a 30a breaker in a custom made electrical box and fed shore power to it then to inverter. From inverter to transfer switch. The dc I ran from the junction blocks to fuse and then to the inverter on + side. On - side I ran from buss to shunt then to inverter. It was a tight complex installation with alot of considerations I'll post up some pics to give you some ideas.