I think running steel line from the tank to the engine bay would be safer. You should be able to find a metric to english fitting at Napa ? Mine here has a whole case of various adapters and fittings.
I went by one yesterday and almost bought a brake line that had the adapters on it. Had the line not been 1/4", I would have. The guy behind the counter wasn't too interested in helping or even pointing me in the right direction. However, I think I may have found the box you're referring to. I should have enough line to run it from the tank to the frame rail. I may rivet some clamps to the underside of the cab to keep it in place.
