What is the car going to be used for? Cruising? Drag strip? What rear end ratio and tire size? Headers? The 302 casting heads have interference issues using some early exhaust manifolds. Your '69 273 would also have come originally with a cast crank. That should handle 300 HP ok if properly balanced and no laughing gas, but, much more than that and I'd want to go forged. It would be cheaper and easier to get to 300HP by using a 318 or 360 as a starting point. Nothing wrong with using a 273 either....I have 3 A-bodies with them running the show! Good little motor, but, it's more a labor of love than being practical.
