According to the FSM it is .024 - .028 for the 1979-1983 750K. You can download a Factory Service Manual for your bike at dansmc.com. I have an 81 750F. The basic service manual is the same but you will find an addendum for the 1980K. It lists the plug gap at .024 - .028.
I rarely use stock settings though as they are many time too short on spark. A longer spark with sufficient energy will produce a larger flame front for more efficient burning and thus the potential for greater power. If you are going to set for stock settings, go all the way out. I would still do .030 though as the coils on the dohc bikes are 2.3 - 3 ohm and produce a hotter spark from that AND from the cdi ignition units than the older points did.
The ride IS the adventure. The destination is just to get gas!