Don,
If your motor tuning is in mm (and it is correct) then just convert the metric entries to inch units (eg. 320 steps / 25.4 = 12.5984 steps) and so on for Vel. and Acc. - remember to save each axis settings before proceeding to next axis. Also make sure Config. / Select Native Units is set to inches. Then test it thoroughly and if necessary make any small adjustments to Vel. and Acc. to obtain the best, 100% reliable, performance.
Tweakie.