I'm not sure what your end goal is for this engine, so I'll just speak to what I can see and what I know from having had a couple. Yes, the 624s are among the least desirable heads out there, and yours are pretty crusty. Assuming that the engine is otherwise stock, the intake manifold is all wrong. A SBC 400 really only has one thing going for it, the long stroke. Otherwise, the rest of the formula kinda sucks. They were low compression, had dinky cams, heads had little potential for performance, cooling challenges, and rod/stroke ratio that didn't help cylinder wear. That being said, they were good at making decent low-end torque and ran on crappy gas.
I'd absolutely pull the heads to see what kind of shape the cylinders are in. If they look okay, I'd be looking for another set of heads -- probably Vortecs. That'll get your CR up and they'll breathe sooo much better. Then I'd pick a cam that suits your needs. Lastly, I'd look for an appropriate intake and carb combo. Obviously, if the cylinders are iffy, it's time to regroup before you've spent any money.
It's a 400 so it makes sense to build for low-mid range torque. Play to it's strength. Resist the urge to build for high-RPM HP numbers.