Thanks for all your help and feedback. It really helped me get my head wrapped around this part of the setup (he thinks).
I haven't been able to properly test this as I'm hooked to shore power and don’t believe a running alternator will throw juice at the house batteries if it senses a shore power connection.
Here's what I wound up doing. If you see anything glaringly wrong, please advise. I'll be swapping my batteries and an inverter out for lithium soon (inverter/charger/Xfr switch). I don’t have to mention how expensive it can get if I got this wrong. The confusion started when the Trombetta had 2 small posts and the LBIM 3. I'll contact Battle Born to see if they have any knowledge and update this post with their answer.
The heavy cables are as you suggest - house and chassis. The rest had me scratching my head. There were low amperage wires connected to the Trombetta on the small posts and one that joined the house battery cable but there were only 4 light gauge wires with one ganged on that small front post.
The wire on the small back post is ground (ground off on the fender well). I wired that to the LBIM Grnd.
One of the wires joined the house battery cable so I replicated that on the LBIM. You can see it on the large right post and marked with a 'H'. It ran towards the dash. I put that back with the house battery on the LBIM. It seemed to make sense. Why would you ask the chassis battery for juice to operate the switch/relay when it's cripple? Something has to engage the switch to complete the circuit and you pray the house batteries are up to the task because the chassis battery probably isn't.
The larger of the two wires mounted onto the small front post was only hot when the engine was running - the one on the bottom with the blue connector. I put that on the LBIM Ign post.
The red wire coming from the relay (small black box on the right w/red, blue and black wires coming out) onto the small post in the front threw about 2.5A when the dash switch was pressed and zero when it was released. I hooked that to the LBIM Sgnl post.
More useless info:
As far as I understand, you would have nothing, a BIRD, BIM or Trombetta not a combination. I don’t know if I'm right. Only what I understand from reading threads on this forum and elsewhere. I know I don’t have a BIRD or BIM. Your larger class A types have those and again, as I understand it, the class C has a Trombetta. The class A's charge the chassis battery when plugged into shore power. Mine does not.
My wiring looks exactly like this: http://precisioncircuitsinc.com/wp-c...i-BIM-Rev1.pdf