I pulled a couple out of mine just because somebody told me I couldn't. Took an real steady hand but there was just barely enough room. It's definitely easier on an old drool tube head.
As Dennis says but if its galled or heavy sludge in the engine then forget it.
AS to the original posters question 66 down heads are the least desirable
as this was the unrevised combustion chamber. They can be modified to work well, however, it takes more time. Generally 70-74 heads are thought of being the best for a race head if you want Drool tubes (they are also the lightest by 6-8 lbs) If you want to use peanut plugs and no Drool tubes the 75-79 are the best.
Frank
