Just did this swap with a 79' swing arm. No drilling of the frame was involved. I still had to grind the 1/2" off of the right side though. The swing arm uses the same style bushing as the SOHC. I did however have to trim a tad bit off the bushing that went into the right side do to a lip that was inside the swingarm tube stopping the bushing from going in all the way. After that I simply used my SOHC pivot tube and bolt to go through the frame (DOHC bolt was too long).
