I had looked at a number of different dial indicators for use in a shaft/arrow spine tester and the one that I found best is this ALLmeter one ...
https://www.amazon.com/dp/B0BN5NR7FR?ref=ppx_yo2ov_dt_b_product_details&th=1No matter what indicator used, the indicator spring needs to be removed so that the plunger is free moving (you can see that in my DIY Spine Meter thread) and you want the plunger head to be large and blunt in order to best fit the shaft/arrow, so the plunger tip is unscrewed, removed.