Your dizy is OK as is. Your spark plugs are OK as is. You will need a 12v coil, voltage regulator & bulbs. Many here say you need a drop to the gauges but I didn't do that when I converted my 55.1 panel and had no problems. Maybe I was just lucky.
BTW you don't need a new harness just to swap to 12v. The 6v harness is plenty heavy (heavier than the 12v). If the existing harness is shot then OK but don't waste your money and time if you don't need to.
