FWIW, the length of stock control arms are 18 3/4" upper, 22 5/8" lower. They're using a pretty well recognized standard length of 23", which combined with stock uppers should get your caster in the ballpark.
If you check around the manufacturers' differ on what the best lengths are for the front arms. Poly's specs seem to be closest to the optimum at 18 3/4" upper, 23 1/4" lower. This gives quite a bit of caster, 5 degrees +, and may not work if you haven't corrected the pinion angle on your housing. A certain (flaming) idiot over on a certain other forum we don't mention around here uses 18 7/8" upper and 23" lower. Grudgingly giving credit where due, he seems to have gotten onto something. I used those specs on a club member's problem child rig and they did work great.
I've mentioned this before but to regurgitate it again, Teraflex for some reason has sec'd some wacky control arm lengths in their instructions, like 19 1/2" upper, 24" lower, with a lower stagger left & right. For a host of reasons, bad handling, component interference, etc. they just don't work and are best avoided. To use the shorter spec with TF's upper arms you have to use the inner mounting holes on the upper arms. Cut off the outer part of the arm or you'll have housing and locker plug interference issues.