IIRC, the only thing that functionally changed between the 750K0-K5 gauges was the mounting screws and their angles (or positions). All the drive ratios stayed the same. The angle of the cable exits changed a bit on the different models, and the K0/K1 units had the OIL, FLASH, NEUT, and BEAM lamps embedded in the gauges. But, they all worked the same, if you could fit them up. Prior to 1972, finding stock to repair damaged bikes was a tough deal, as Honda had a hard time making enough bikes, let alone spare parts.
You may find that changing the silver rear cover will present the proper mounting holes and angles to almost any of the 750K series gauges.