I have been using a snap gage for years.
It gets the job done. I do have to be careful since the snap gage diameter can interfere with the step in the retainers.
And similar with the valve spring pocket in the heads. So try not to have the snap gage at an angle.
I should just buy the spring height micrometer, but I have read some not so good reviews of the less expensive ones.


1993 Daytona, 5.50 at 130mph (1/8) 1.19 sixty ft (PG). Link to 572 B1 - Part 1