Measuring OMC shift rod height

[Striper80]

What's the best way to measure shift rod height on a 98 Johnson lower unit? The PO had an SEI lower unit installed on my 22WA a few years before I bought it. When I changed the gear oil I noticed a lot of metal so I sent it to them. They said the reverse clutch was shot and they replaced pretty much everything for me, under warranty thankfully. I have to check the shift rod adjustment and I want to make sure there's not much margin for error. Unfortunately I don't own the tool for it.