First and foremost, I am not an expert but have rebuilt three (3) engines to stock specifications so far using Wayne's book, the Bentley and Porsche Factory manuals as well as the information found on this forum.
IMHO, I would say "Yes" that you should check the Deck Height. Why?
Because of a couple components which have changed in your particular build, one being the 1978/1979 factory pistons are 8.5/1 CR. Your new Mahle setup is 9.5/1 CR which means some significant difference with the shape of the tops of the newer pistons.
Also, you have changed the Cylinders so one question that comes to mind is: Are the newer Mahle cylinders of the same height group ? ( Hint: check the KS cylinders and look for a triangle with a number in it.) Is it height group 5 or height group 6?
I believe you would want to be careful and do the Deck Height checking because in Wayne's book he states that this procedure should always be carried out "when any of the components have been changed" with the build.
Just my opinion here, so if it were me "yes" do the measurement to be on the safe side.
As mentioned above, the alternative could cost many $$ to fix should there be a problem with valves hitting pistons on start-up.
Hope this helps and "Good Luck" with your engine.
