Ian,
If your transaxle has been relocated rearward then this modification must been utilized. Some "extensions" are more glamorous than others.
Mine isn't the most pretty thing but it's damn strong.
If your car shifts well, with the current ugly extension, then I'd focus on getting the extension rewelded and call it good.
Hose clamps are no way to go.
Seriously dude. Stay safe the best you can. We need all of the 914 owners we can get.
Roger