No, they won't fit I'm afraid. and if you are putting into a RHD, which being a fellow Aussie I'm sure you are, even the tri-y's from a LHD 450SLC 5.0 or 500SLC won't fit, either. ALos, if putting an engine from a W126 in, he will have to change the oil pan, to fit around the 107 subframe.
There is a chap named Hendrik in Estonia that made up some custom stainless headers for an R107 some months ago. He mostly does his thing for W126 cars, but his work has a good reputation, but he may want more validation before he starts selling units. I'd check with him for your specific RHD specific clearance issues and find out what he can do. Several South African/Namibian buddies have a similar challenge on their RHD R107s, it's a bugger to solve without a custom source. Other than this source, there is always taking your chances with a local exhaust shop with the equipment to do mandrel bends, have them demonstrate this by the way, and ensure they can really make the clean cuts neat, gas-tight MIG welds with them. I find the chances are generally poor; one in a fifty shops seems up to the task, maybe less.
Hendrik has an associate in Sweden where he sent his headers to test out fit and clearance, since he didn't have an R107 locally to try it out on. Drop him and email and see what you find out. I'm not sure he's done a right-hand drive R107 as yet, so depending on success with the first try, he may be game to do another. [email protected]