I am going to go against the grain a little and say you do not need a dial bore gauge or inside mic unless you plan to do a lot of measuring in the future.
The snap gauges and micrometer shown in the first post can get you within .0002” or better when used properly. That method was used for years. Just make sure the snap gauge is level in all directions, and the spring loaded ends are pointing up and down if the block is level upside or upright. Snug the lock when satisfied you are at the widest point vertically, then measure the snap gauge with a micrometer. Do it a few times and you will see how repeatable and accurate it is.
I am not against buying tools that work well, But no need to spend a bunch on a one time use tool if you already the snap gauges and a 2”-3” micrometer.
No matter which method you use, be sure to measure vertically. If you rotate the tool away from vertical on a new bearing, it will show wider readings, by design. The specs are for vertical clearance.
