The jugs aren't exactly the same but they're the same if that makes sense haha, they match up a tiny bit differently but they fit, im not too sure about putting a 650 head on a 750, im putting a westcoast 750 head on my 650 and the domes are wider than my cylinders which i think is okay but im not sure if you want the domes smaller than the cylinders which would be your case.
So im not to sure if you can but thats my 2 cents, hope it helps.