Installing sight tubes on my Model III was pretty easy. I used rubber grommets , push-in 90 deg elbow fittings and Bing blue fuel line with brass rod inserts. Developing the placards to go behind the gauges was the most time consuming task. I made aluminum backing plates, calibrated with a paper template, did the artwork and had them made up at a vinyl sign shop.

If you want to go that way, I can provide sources for the parts I used.