SRT is a a different unit and does not match the picture in the parts book. Jobber cost for a reman unit form the local mercedes dealer is 1250.00 per side that includes pipes and both front and rear cats. And yes they are hard to come by.

When my rears decided to blow like the sands on the beach, I went and searched and wound up at my local muffler shop and sourced two small high flow cats that fit. It is really tight up near the engine with not much wiggle room. If you check the bracket that hangs the exhaust between the rear and front cats there is a MB AMG part number there, it is the same as the slk32.