Using Autometer's 9123 on a factory 69 tach

[F'in mine]

Just wondering if anybody has used Autometer tach adapter harness #9123 with a factory tach on a 69 Camaro or other GM era vehicle with any luck on there conversion?
https://www.autometer.com/ls-plug-pl...h-adapter.html

They cannot guarantee it will, any first hand knowledge would be helpful, tks.