i did it on my 87 wrangler front end. you have the split axle on the passenger front side with a collar that slides over and lock it together when you put it in 4x4? thats the vacuum actuated part you want to replace, correct?
i used a cable that was a generic choke cable for a carbureted engine to pull the pull the collar back and forth.
let me find some posts and i will link them for you