Here's my opinion, and I should say that I've modified rare cars, restored rare cars, modified "normal" cars, and been around race cars, historical cars, etc for decades:
Curious yellow 4-spd A/C Roadrunners are beyond rare, probably a single-digit amount were made. That means it's very valuable, and extremely cool in stock form. That body is also pretty heavy, and not even close to the best platform for the kind of performance you seem to be after.
Stick the big motor in something else - earlier B-body or '67-up A-body - and it'll be easier on drivetrain parts and you'll have the best of both cars/worlds. And you'll have one of the rarer & cooler Roadrunners on the planet.
Lumpy cams & A/C aren't very compatible anyway, and you'll find that the lumpy cam in your imagination won't be as driveable in real life stop-&-go driving. I learned long ago to make the hot rod the hot rod, and to maintain the rare stuff intact.