fuel gauge folly

The meter match has its own VR built into it. I dont think you can run it off your own existing VR. Maybe im missing something here, I dont know. Do you actually have any experience using a meter match?
I dont know of any high current version of the standard (TO-220 package) 7805. There is a low power version, 7805L which should not be used for this application. A good option would be the TO-3 7805K 7805K Voltage Regulator - Twisty Wrist Arcade and Pinball Parts regulator but they are getting hard to find and mounting it could be an issue.
But yeah, a standard 7805 would probably work with a big enough heat sink. On a dash like an E body its easy because you can use the aluminum housing to sink to. The good thing with the 7805 is it has internal protection so if it gets too hot it will cut itself out and reset when it cools down. They are fairly tough to kill.