LA 318 advice
I had a lot of success getting more out of a 1970 318. I didn’t go crazy because there wasn’t much out there like today. A few things worth mentioning:
You mentioned using your heads. Take an intake gasket and exhaust gasket. scribe the ports. 318 engine heads are sloppy. If you’re not in a hurry and into it port your heads with a set of carbide rotors filed. This was a huge improvement.
I used a 273 four barrel carb. It worked great out of the box. Dumping big carbs and cams in a 318 is in my opinion a waste without heads that can flow. OR better yet slap a set of 340 or 360 heads on if you have them. Dodge vans had 318 engines with 360 heads. Chrysler did this and it worked great.
Without mentioning a bunch more I think balancing an engine even stock is worth it. Chrysler was not great at tight specs balancing their engines so it would be an improvement no matter what.