| As far as I know, performance upgrades for these cars are limited and the results of making special headers, head porting, compression increases and induction modifications, etc., would be marginal, at best. In addition, they would be expensive. The car is heavy and lumbering, and could stand a substantial improvement in the chassis/suspension/brake area. Further, I'm not sure the 3 speed transmission would be up to the task of a quantum increase in HP. If keeping it "stock" is not an issue, the 4.5L engine is rather large in size and I'm sure the engine compartment would handle a modern day firebreather, quite nicely; which would also give you some better transmission options -- with the added bonus of better gas mileage when you don't have your foot in it! Crate motors, from various manufacturers, are a lot less expensive than anything MB has to offer, you can be sure of it, and the performance increase would satisfy the most demanding desire for speed. At first glance, grafting in an engine does not seem to be that big of a deal on this car -- though such action may be seen as a sacrilege by some. The bottom line: it's only a matter of money.
I've pondered the same ideas myself, not being as impressed as many by the "superior German engineering" mantra, but have opted to keep my car original and stock. There is something very endearing and classic about this car, the older it gets. I have several other 'toys' which have undergone the "treatment," and allow me to satiate my wreckless moments.
Cheers! | 
