Actually the FSM says .008" to .018".  I just set mine up and it feels good.

But we old guys and you Phucker should just do it by "feel" I never cracked a manual to look for that one.

"Push-pull" is my method.
I guess a younger "Auto Technician" can hang a dial indicator next to the axle and get it within +or- .002 of spec.

I have to comment that the seals are backwards, according to the factory manual. the larger foam seal is put on the housing then the brake plate then the steel gasket is between the retainer and the pate. This is because the foam gasket, is an outside water seal.  The steel gasket, gives form to the set up, under the retainer, for no wiggles.  KEN

Believe , me when I say that it probably doesn't matter, as far as wiggle room. I look at the few diagrams in the 1974 and all have the larger gasket between the backing plate and housing, BUT the instructions SAY "foam under axle retainer and backing plate". I can't remember how they were from the factory anymore.
     I'm thinking that the gasket that came with the RP 400 bearings, that I used under the retainer, and similar one between the housing that squished was why my seal leaked. (On another thread I posted.)
  So it is important to use the factory types. Sorry for the attack but this is my hell today. Feel welcome to reason this out and correct me. KEN