The o-ring for the throttle body to be mounted to the NA grooved intake manifolds is
https://needswings.com/throttle-body...g-m112-or-m113
well, that is our version of it as we have them in a higher quality Viton rubber.

The "twist" spacer / gasket above is for the srt6 supercharger (not even used on slk32). they used to be $12 until Mercedes used them on the SLS and they jumped the price.

For the original post. yes you can pull the 74mm throttle bodies from eBay or junkyards all day long as Mercedes made several million cars with them so the market is there on them. The used TB's we sell we get in from srt6 or v8 Mercedes customers that then decide to upgrade to an even larger throttle body and we take their old 74mm tb's in on trade, I have more coming in than going out so only the better ones make the grade. I will not bother with ones with oxidation on the housing. Knowing their history gives us the piece of mind knowing they came off properly running cars and the confidence in them to pass them along to other customers. I sell very few used electrical parts, intentionally from experience, this scenario is one of the exceptions that I still allow due to the success.