[Weldangrind]

Remarkable! Did you stitch the leather on a machine? I want to learn that skill. Please show us a pic from the side with the seat installed.

I would remove the gas cap and fish a piece of wire up through each tube and see where it comes out. That should tell you if one is a breather, or if one is reserve.

Dave just cleaned his tank by soaking it in vinegar, and I've heard that apple cider vinegar is the most effective. After you rinse it out, be sure to blow out as much air as possible, and then slosh some sort of lubricant around inside the tank to prevent flash rusting.

If both tubes are meant to be fuel lines, the shorter one is reserve. You'd either need two taps and filters, or one switchable inline tap and one filter.