Appears to me that it is a CB750, 1975 model, built in 8/74. The frame number (which you showed) is the number it must be titled under. IF the p.o. titled it with the CB750E number (found on the top of the bottom end of the motor, under the left hand carb) that's only the number of the engine, and you may run into problems at the DMV. I have in the past.
To answer the rest of your question, it is specifically a CB750 K5. The F model was available in '75, but you don't have it.
Good luck,
Chris in Boston