Ha Ha Delkevic supplied by father & son team Derek & Kevin Neesam of D.K. Motorcycle breakers fame in the UK ... hence the amalgam of the two names (i.e. 'Del'=Derek, and Kev ) in the UK. The guys responsible for shipping literally thousands (probably tens of thousands) of Japanese bikes across the pond over the past 30 odd years.
This video from 9 years ago shows their showroom from that time, including my green '69 CB350K1 I got from them, which just happened to still be there waiting to get picked up.
Reports of the repro pipes I have heard of are really good from UK people I know. If they could reproduce CB400F double-skinned headers (like the short run that Sankei are doing) that would be a game changer.