The rocker ratio is 1.39 to one.
My dial gauge is only 5mm throw, but it works OK. A 30mm one would definitely make life easier though. The lift at the cam would be covered by a 10mm gauge. ( A 336 has about 10.5mm lift at the valve so only 7.5 at the cam.)
The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt.