Difference between lobe lift and pushrod lift

I am simple bringing this out so it can be taken into acount when choosing camshfts. A racer friend bought an expensive roller grind for his W2 small mopar. The heads flowed 307 @.640. so he ordered .640 lift cam. I degreed it in for him and as installed with 1.5 Harlin Sharpe. He only had .598 at the valve with lash. Heads flowed 287 @.600 . He was not using all of his heads. Using the Superflow formula, he was loosing aprx. 41 H.P. with wrong cam. Car went best of 10.37 @128. but 10.40's most of the time. I ordered him a grind that would give .645 at the valve as installed with lash. No other changes the car went 10.11 @131 off trailer without tuning. Just a word to the wise will suffice.Terry.