I’ve had good results taking the largest and smallest dimensions, and using the difference as lobe lift.
It doesn’t need to be down to the thou accuracy since there is a fair amount of lift difference between the factory cams.
For example, I have a used replacement SB cam here.
No numbers on it.
Measuring both an intake and exhaust lobe with a caliper showed .271 lobe lift on both(1.616-1.345).
This is very close to the 360 low performance/2 bbl cam that’s .410/.410 lift.
Edit- I put the cam in the lathe and checked the lift with an indicator.
I was pretty close with the caliper measurement……..it was .273 when checking the same two lobes in the lathe.