Looking good, well done on a lot of work.
I have been doing the 550F1 and thought it would all be finished by May, but it's missed the Summer and will wait until next year before getting it on the road.
Just starting on my 1978 K4 (didn't know there was a K4 until recently, but I think it is identical apart from seat). Hope my silencers are intact (they are Sankei,s, I presume not original, but aftermarket) as it's a shame to patch or put a 4/1 on it. But replacement is an expensive add on at the end.
What paint did you use on the crankcases and block?