Yes, I have an 88 300E with a manual transmission and it's a jewel.

I think though that your SL is an M104 twin cam engine, not a M103 single cam, but I might be wrong.

I reread your post and it sounds like your SL is a Euro car which I suppose is an M103. Sorry for doubting you.

I have spent almost 300,000 miles in the drivers seat of my manual transmission M103 car and I share your love for this drivetrain.