Cruising on the highway at 75 mph without towing a trailer or being packed to the gills, that Cadillac 472/500 can easily get 14-18 mpg. Around town, 10-12 mpg is more like it.
Another vote for the 472/500 is that there are lots of performance options available for it similar to the stuff you can do with a SBC.
They'll even sell you a complete 500ci engine built to your performance needs. One of their categories is Street Rod/Classic Truck
https://cad500parts.com/
