Most 540 equipment is on a 6 spline 1 3/8 shaft.. If you have 15 or 21 splines.. I'd check rotation and speed before i just bought an adapter.
Who makes powerking? And waht hp is it / category? Lots of class 2 tractors that are 80hp and up are either 1000rpm pto, or selectable for either.. etc.
I had a valmet once that had a 540 pto.. but was multi-splined. Was like finding hens teeth to get the correct adapter.. course this was 16 years ago..e tc.
Soundguy