225 6 to 273 8 swap

welcome!
the 273 will fit, but you either need the v8 k-member with those v8 mounts or some conversion mounts for the /6 k-member from someone like shumocker. Correction: just need the mounts. The trans will not work as the bell housing are different. The internal parts are interchangeable. dart and valiant engine bays are essentially the same on most of the early a's

Where in Ohio are you, the mopar nationals are in a couple of weeks near Columbus