What would I gain from a 4bbl on a 273?

Carbs are alot like socks or underwear. Whatever you like. IF it were me doing a 4bbl on a 273, I myself would do the Edelbrock 500 cfm AVS. Everything else is stock minus the dual exhaust right? Even with a small cam, that should be enuff for the street.

If you plan on pumping it up and start to create some HP under that there hood, Holley has a small street Avenger 570 cfm that would do well. Also a Edel. 600 cfm on a hopped up engine is a good size.
Over 300 HP for the latter carbs mentioned.

The small engine doesn't need to much cfm and would be a bit muddy down low with a carb to big.