How is it possible to install parking lock cable on a 65 904?

Yeah I've got the factory manual. If you try to do it the way it says I can't do or see how it's possible to get everything connected and disconnected through the small park cover allen head screw. You have no idea if you're touching the lock spring or not so you may as well unbolt the cover to see it. The problem comes when you have to reinstall it. I can't figure a way to make sure the adapter is locked in the parking pawl. I don't see how it's possible to do it through the allen head cover screw because it takes a good bit of force to unlock the adapter lock spring. I doubt even a local transmission shop would be able to figure it out. If there's an easy way that someone knows how to do it, I would like to know.