I know how you feel. I am rescuing my grandfathers 1973 450SL. The car has not run properly for sometime. Thanks to this forum and some work I should be driving it to the shop today to be fine tuned. These cars are prone to rust. Check the rockers and the rear wheel wells. They DEMAND regular maintaince if you get an early 70's car you will want as complete records as possible. If the car smokes it needs a valve job. The dealers were charging $1600.00 a few years ago. If the fuel gauge is not working beware we just had to flush the gas tank after the old sending unit rusted, there was tons of it in the tank it is amazing the car will run at all. If you are willing to get your hands dirty these cars are great fun. But when they get in trouble they can drive you nuts the best thing above all is find a good tech to work with. When this car is maintained by someone who knows the car it is a real joy to drive.

Regards

Charles D