273 upgrade to 4bbl?

IMHO....upgrading to the new intake and four barrel will absolutely add some "spunk," as long as you don't overdo the CFM output of the carb you use. If it was my choice, since you have the intake off, pull the radiator and then the timing cover, valve covers and push rods. Pull the lifters, chain and the cam. Shop around and get a cam and lifter kit to match the type of performance you are looking for. The folks at Hughes (https://hughesengines.com/TechArticles/2choosingacam.php) are great to work with and can hook you up with what you need. The folks at Competition Cams are great also. BTW don't forget a new chain. Sounds like a lot of work, but it really isn't. Have fun and enjoy the outcome.
Norm