The cab shackles once you have them rebuilt can be shimmed see picture for how shims look. If you have not removed them the original shims will be there so you can see how they were arranged. Measure from the frame to the bottom of the cab in back you just need it level there once everything is tightened down.
http://good-times.webshots.com/photo/2235943390102454676FUuGUv
Shims can be on frame or cab bottom I have seen trucks with 6 and trucks with none. Lock plates go inside cab behind seat pan.