Ohlins shock spec:

2006 CBR1000RR Length 314mm (+6) Stroke 58mm Spring 685 lbs

NSR MC21/28 Length 302 mm (+6/-6) Stroke 50mm Spring 742 lbs

NSR MC18 (measuring my old shock) Length bout 280 mm, spring ??

So CBR shock is little too long for MC21/28, however taking 8mm out of stroke will get you close (306mm)
it's under-sprung so will need new spring and valving and also it has attached reservoir that might clash with subframe.