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

My 66 dart gt has a stock 273 in it and I'm planning on dual exhausts this spring, along with electronic ignition. Would I gain much by also installing a 4bbl carb or is it a waste of time and money? I don't want to stray too far from stock.

Also, what is the relationship between horsepower and torque? I've noticed early Buicks carried a high torque rating relative to hp. Is it possible to squeeze more torque out of this motor?