I have had a fair few Honda 550s in my time, and found that quite a few parts are interchangeable.
The front mudguard from the K3 looks a lot better without the front stay, and cleans up the lines on the F2.
The Stanley H4 unit from the K3 fits the F models nicley, and makes a world of differance.
The early F1 rocker covers where not as good as the later ones as the early covers used one rocker shaft per rocker,as against on e shaft per two rockers.I found this out because of a strange noise coming from the top end that I could not put my finger on until I stripped off the cover and took it apart.
The 35mm OEM fork seals from the 750F2 are a better fit on the 550 models,as they have a double lip.This causes slightly more stiction,but then the forks are a fairly old design anyway.
As I remember other bits that are interchangeable i'll put them up here.
