The diameter of the thread is 1 1/32" but I don't know the pitch. The dia on the top of the tappet guide is 1.130" , so it could be done.
The problem is that the angle on the WR exhaust tappet guide is 3.533 deg. while the valve angle on the K models is only 3 deg. which means that over the length of the valve cover they will be out of alignment by over 1/64".
I would expect that this would not work unless the threads were to be made extremly loose and even then the threads would be apt to cross thread as they are not very deep to start with.
The intakes would be less of a problem as the angle difference is only .033 deg. and would probably work.
Even on the stock K's these can be troublesome to screw on!
Check out my website. I do make WR valve covers that are direct bolt in and can make them longer to fit the KH.
I am also just starting to make longer tappet adjusters to use with the KH cylinders.