1970 Dart Cluster Removal

The homemade 7805 based regulator will work but... fuel gauge needle at switch on will be slow as molasses, both gauges may read a tiny bit off. I said may because all 7805 regulators ( and heatsinks ) are not equal. The hotter they get the more voltage they pass. One might start at 4.8X and climb to 5.2X as it heats up, while another brand/lot starts at 5.0X and climbs to 5.5X as it heats up. Anyway...
RTE builds the closest to OEM operation in solid state replacement.
And just so you know, you most definitely need a dedicated ground wire for homemade. The 7805 alone does not have ground fault sense. It will pass 12 volts to/through the gauges if it isn't grounded. Test to prove this on your workbench if you want.
Just another way the RTE package is better. They include ground fault protection in their circuitry.