On a lighter note the bore sizes of the coupling fit are different, if the differance is only small you can use a larger clamp and stretch it to fit but if its a big differance is size then you will have to modify the pipework to make it fit.
This would normally involve using a reducer pipe or welding, maybe both..... Not too difficult if you have the right tools for the job, if not then its a bit tricky.
Hope this helps ?????