Denny,
Frank McGurk's 1953 booklet on the Chevy sixes has a plot showing the valve lift to be 0.300" for a stock camshaft. As the valve lift duration (and opening and closing crankshaft angles) matches that which is shown in the
1948-51 Truck Shop manual for the intake valve, it may be safe to assume that Frank's plot is for the intake valve.
Of course, as mentioned above, if the cam is out of the engine, the lobes can be miced for relative cam lift. If the engine is assembled, the lift and duration can be measured at the valve with a dial indicator or other suitable instrument.
Hope that this helps.
Hoyt
