you could ad electronic fuel injection to the stock motor, cam it and gear it and the owner will forget about the 30 mpg while he's grinning ear to ear!. IE restomod. Or pull a 2.7 ecoboost out of a wrecked Mustang 21/30 mpg. A tune will ad 60hp if he wants a little more.
https://www.ford.com/cars/mustang/
