For toe-in measurements I setup a parallel string arrangement. I place two bars, one in the front and one in the rear. Each bar has two slots cut, one at either end (note: the slots were cut into the bars simultaneously to ensure that they are exactly the same distance apart).
They are set on jack stands raised to set the string at wheel center height. Knowing the front and rear track widths, the strings can be set to parallel by measuring off the wheel centers. For the Suburban the front track width is 1" narrower than the rear so I adjust the strings until I have a 1/2" difference in "depth". Since the string slot distances are identical on the two bars getting one side parallel ensures the other side is also parallel.
From there it is a series of measurements from the fore & aft edges of the rim at the wheel center height.
Camber is checked using the framing square and measuring from the top & bottom edges.
Screenshot of the calcs:
Since the rear wheels are fixed (i.e. no toe adjustment possible) I use them as the reference for calculating a "Reference Misalign" measurement. This delta (rows 20 thru 27) is then used to calculate the corrected measurements for the front.
Not shown in the pictures are a set of greased linoleum plate pairs for use as turntables.