Propane or gas pick one not both.

My old neighbor had a duel fuel 460 F-250 and was nothing but issues burned the valves up towing his 5th wheel on propane then had it rebuilt specifically for propane. If you try to run both fuels its never making the best of either.

Not to mention he'd run on propane for months and months then try and switch to gas and all the issues with old fuel and dried out parts in the gasoline side of the system would show up.