I'll second that stuff like gauges for those older tractors just don't have the quality the originals ever did. And the price for some of them is outrageous.
For the late 20 series with the fiber optics dash lighting, the mech temp guages are now over $200 Can. Most I seem to get out of them is a few years at best.
As for the fuel gauge and float, one that would fit both the tank and dash would be the ones for the later models, which were all straight 12V. Only problem is, the gauge won't have the hole for a light bulb, just a small one for the fiber optics cable. Anything for a 4020 s/n 250000 and up will be of that style.
Contracts are made to be broken, a handshake is the law of God.