Old Camera, Older Lens

Hello, I took this picture of a friend last October using a Fuji S5 Pro that came out in 2006 and a Nikon 105 2.5 K that would have been new in the mid 70's. I love this combination for portraits but sometimes it's hard to focus. Has anyone tried a Katz eye focusing screen with their camera and what do you think of it. Thanks in advance. Terence