My two cents. I had a 69 340 in my 72 van and used all the 72 attached items to make the motor look stock. You could not see the timing marks because they were hidden under the later year items. I always timed by ear and it ran great for 40 years. When ever I had to remove the disturber, I would place a notch at the base of it and also mark the block, so I was close to where I had to be, then use my ears for final adjustment. I have seen many old-style (Craftsman's) timing lights at garage sales for 5-10 dollars.