Remove clutch discs. Measure between piston and snap ring.
Then measure stacked cluches and pressure plate. Substract from measure taken from clutch.
Or Make measuring gauge from wire of suitable thicnes. Hammer or file to fit the gap then measure with caliper.
Neutral creep is caused by too tight forward clutch. Set clearance to 0.04" you should be good.
On direct use factory spec or 0.06".
Pressure plates can be turned to gain clearance.
Forward lower plate can be modified to gain clearance to direct pack.