I have the 10.5 inch clutch and used d450s in my barracuda with a 360, it all fit. However I got all the needed parts from Brewers except the bell housing which I already had. You need to use the clutch fork for the d 450's. If you go to summit look up d450's, look at the instructions on the last page they give you a part number for the clutch fork. You will also need to use a mini starter. If I had to do it again I would use a mini that is clockable . I am pretty close to the header pipe
IMO if you already have the 360 and spent the money, find another car to put that 360 in. You have a very special rare car. If it came with the original 273 Keep it, and try to build it up to make more horsepower if that is what you are after.