The thrust bearing is integral with the rear main bearing. The only way it is 'adjustable' is by grinding the crankshaft.

Really it is just a matter of checking on assembly. Neither the B18 or 20 are prone to thrust washer problems. I have always found that if the crank journals are seviceable then the thrust is OK.

Twice I've run into trouble, once with a car I bought with a fully reconditioned engine that had loads of endfloat in the crank because it had been ground wrong, and once with a B18 that I bought in bits where the journals had been machined but not the thrust on the crank, there's usually a reason if something is going cheap.

I've never bothered actually measuring with a dial gauge on assembly. There should be no perceptable end float with new oiled bearings with the caps torqued down, nor should the crank lockup. As far as I know there are no options onthe size of the thrust, from memory the amount machined off the thust face of the crank is 10 percent of the amount machined from the journal (don't take this figure as gospel).

Regards