Hello Rocket,
Your first post, so welcome to the Group !
Well, as to your question ...
I am not aware of the 180 051 78 01 cam.
I only know of the 180 051 76 01 cam (early M127II, 230 SL) and its today's replacement 180 051 84 01.
Also, I have not seen yet that there is anywhere a full "parts" number on the camshaft. Have mine out as well and will have a look at it the upcoming weekend.
But ..
if you found already the "76" on the rear of the camshaft, this means you have a 180 051
76 01 cam, which is supported by your production date 26.6.64 (= 26 June 1964).
So, that's the correct cam for you.
Best,
Achim