Hi,
I have a Haynes manual which does cover the 230,250 & 280. It is good but not great for a 230SL. I think it is more focused towards the 280SL
For example, it only talks about disc brakes on the rear and my 1965 230SL has rear drum brakes. Your '67 car might have disks. There were many, many upgrades over the years even on the 230SL so no manual will be perfect.
I also have the Autopress Mercedes Benz 250 1965-68 which covers the 250SL. That is good but is not focused on the 230SL (of course).
I recently bought an Autobooks Owners Workshop Manual for the Mercedes Benz 230 1963-68. That covers the 230, 230 S and 230SL and is very good (and covers the rear drum brakes well).
I am in the middle of a significant brake overhaul job on my 230SL, hence the brake obsession !!
I also recently bought a DVD copy of the BBB. It is a very large PDF file. Difficult to have beside you when you are working on the car but has good search facilities and was a lot cheaper than buying the hardcopy BBB.
Be careful which BBB you are buying as they were updated every few years and you want one that covers your car but not the 250SL or 280SL.
The BBB is very technical and quite difficult to follow for amateurs like me. However it has every piece of detail you could ever possibly want (and more). Also, it reads like it was directly translated from German and so is a somewhat unclear.