Good news for those of us with window handles but no knobs. The original knobs were a bit of bad engineering as it used a brass swedged fitting to hold the knob fast. That's why they all come off eventually. Thanks to our brethren in the Datsun Roadster world, replacement crank knobs are available for 67s and earlier - the design changed in 68 so these will not work, I think for the later patrols.
Here is a sided by side comparison, they are exactly the same (apparent difference is artifact of how I held the camera)
The kit includes the knob, washers and a tube of locktite
Installation was super-easy here are the results:
$17.35 for one $28 for pair from Datsunparts.com, part #1345
http://datsunparts.com/1345
Also check out their assortment of lights, choke and throttle repro knobs.