Here’s a thread about compatibility issues with Nimbus/KH hubs in Impact frames. If I remember right the flanges on the Impact hub are just a little closer together leaving a bit more clearance for spokes to the outside than KH. As a result the Impact hub fits in the KH frame, but the KH/Nimbus cause spokes to hit the Impact frame. There are some pix of Impact frames that have been filed to clear the spokes.
At the end of the thread there is a post that says it all just fit together, so at best it might work but don’t count on it.
If you want an Impact frame just get an Impact hub. Of course if you get a KH frame anything should fit right?