Confused newbee with a 273

Ok.. gotta fess up... been a Chevy dirt track guy for over 20 years. Sold the dirt car and bought a '67 Cuda with a 273. Long term is to wind up with a 318 or 360 Magnum. Got an opportunity to buy some nice looking coated headers that came out of a '69 Charger with a 318.

I'm confused about any difference of the 273 vs. the rest of the LA heads. When I look up part numbers on Summit or JEGS for the Charger and the Cuda with the small blocks, the part numbers are the same?

Will the Charger headers fit the 273? Will they fit the eventual Magnum?

Boyz... I'm gonna have a lot of questions !