[tofgasp]

You do not really care if the ratio vary between one rocker and another when timing the cam, the gauge pointer is set 90° on the valve retainer so whatever the ratio variation is, the timing can always be set properly.

It 'll be surely easier and less prone to misreading with a 30mm gauge, but you mostly need to check precisely when the valves begin to open/close (priority on intake closing for the setting), so the max lift is quite useless.

The 30mm dial will be usefull for setting your disc on the TDC first, most on them have a screwed ball pointer that can be repraced by a threaded extension. Check for the same measurement after and before TDC, the real TDC is the average of the two. I've found this really the most important point of the settings.

For info I checked 10,7mm lift with a 336.