My present setup has the starting current going through the 1-2-both switch... so certainly it can handle the current.

So really the setup just needs to involve resizing my house battery bank so I have some long term house current there. Then I just switch the batteries for whatever need I have at the time... either starting and running the engine, or running the house; with the "both" position such that I can combine both house and start, should their be some battery failure.

So I really only need to change the battery boxes and get some different longer cables, and relabel the switch so it says "house" and "engine." I want to run some group 31s for house and probably that group 24 for start. Sounds a lot easier than I was thinking. (see what happens when you post BEFORE the morning coffee...)