Seems there are lots of options out there now for fuel systems to build one to fit your needs. Holley has a drop in pump/sender now that fits the stock tank and is regulated and returns inside the tank itself. I believe its a 255L flow pump so its good for stock or mild motors. If that pump fits your needs I think that would be the way to go on a cougar. Obviously if you need more flow you would have to go a different route but lots of options for that too from replacement tanks or retrofits for drop in pumps.
Agree on the sump system. Bad idea all the way around.
Im glad the EFI has become much more cost effective and easier to do then ever. I really do hate carbs 