thanks, peder, for the reply and warning.

I would not run propane thru any of the existing gasoline fuel components.

And I now understand that an extra 12V cutoff at the tank would prevent LPG in the lines from returning to the tank when the vehicle is shut off, so that's probably not safe either.

Which brings me back to how multiple tanks are generally plumbed together. The liquid service have some sort of overflow check built-in, but without backflow prevention, what keeps fuel from 'equalizing' between the tanks when filling? obviously, one can manually shut the service valves when filling, but that sort of defeats the purpose of a remote-fill setup, doesn't it?

Still trying to put all the pieces together in my head before I have my local propane guy help me get this conversion done...