This may help. http://oljeep.com/gw/vac/axle/83-84-...ePictorial.jpg
Essentially vac is supplied to the front axle motor "first" then to the tcase shift motor. On an 83 ya gotta be stopped before shifting from 2WD to 4WD. Hence the reason for the pull pin on the dash selector. Requires 2 hands to insure you're at a full stop.
If interested in buying a factory original paper 83 supplement, PM me and I'll dig around, I should still have one around here somewhere.
On side note once you get new vac lines installed and the front axle isn't engaging it's likely frozen. It's actually a decent system but prone to internal corrosion from lack of use. Especially in a humid environment it's a good idea to switch to 4WD and run it a few miles monthly or so to keep the corrosion to a minimum.