I've got this if you are interested. I bought it from Devon after he bought it from Jim. I have to be honest that it's not as good as the pictures make out but the frame had been powder coated and the engine rebuilt. The silencers are in really good condition too. The rest of it needs a good sorting out. I'm only offering it here as I need the space and I've got too many projects on the go. Because of the drum brake and the pea shooter silencers I've good reason to believe its a 1969 CB450K1. Although it's got a dating certificate for 1971, everything on it except the tank points to a 1969 model. The more rounded tank wasn't fitted until 1970. That model (K2 onwards) also had a disc front brake and megaphone silencers. The bike comes with a few spares and if you wanted to make it into a Black Bomber look alike I could help you out with most of the parts required (for a fee)!
I'm asking the £850 which I paid to Devon. Good K1's a fetching almost £6K now!
I'm not too far from Swansea if you want to come and take a look.
http://www.ukgser.com/forums/showthread.php?t=326610