Congrats and welcome to the club...............I've been known to pay more. Your entry cost is envious. Yes, we are waiting to see the tank and clocks.
A nice 4-1 exhaust looks good until you want to spend the big bucks on no-number pipes. Please don't attempt to ride the bike before you fix the front brake. Also note the bent rear rim. Yes, you K0 has a few parts from later models, but the frame, motor (running) title and the parts you have are worth a lot more than you think.
The primary reason the K0-K1 bikes are regarded as 'faster' is the combination of internal and final drive gearing along with a slightly more aggressive cam and timing. A good trick to 'straighten' that bent fin is to lightly wedge a piece of hard wood or hard rubber between the fins and then run the motor until very hot (10+miles). Then gently push the wooden wedge further in but do not over-do it. Then ride a few more miles and try to get it close but never go more than the original. I would leave it very slightly upward to prevent it from braking off. Leave the wedge in place until the motor is cold.
You'll be a hero on this board when your finished saving the bike. It does not have to 100% stock to be a 'hero' project.