273 to 340 swap in 65 dart

One other thing is what bell housing do you intend to use? If you use the one from the 340, you will need a flywheel and clutch and presure plate from it. If you use the one from the original car, it might have trouble handling the power from the 340. The 340 or newer style bell housing uses a 10.5 in clutch and is a very tight fit in an early A. The fire wall to floor lip will have to be foldfed back to clear the larger bell housing on your car.
Other than that you have most issues covered.