Quote
Should the shims be on there or are they to be used only if there is extra play in the shaft?


Take this with a grain of salt since I've only done this on a 93 Rodeo (read: 1st gen Isuzu). The axle should have some play - thus the reason that you need to jack up the wheel in order to get the splines out far enough to get that snap ring on. Thus the whole reason behind splined shafts, actually.

Shims in a hub? Never heard of it...