[Dave at Pelican Parts]

The 914 calipers are different early to late. The change happened with model year 1973. Actually, the change happened very very early in the 73 model year--I know of a couple of 73s with the early non-hub-centric hubs and wheels, which means the early brakes as well.

The mounting plane is different from early to late. I think it's a 1/8" difference, but I'm not sure. What I hear is that the 320 calipers do not require machining for the early struts, while they do for the late struts. (Check the 320 tech article for exactly how much gets taken off.) If this is indeed the case, then the amount of machining called for in the 320 case is the difference between early and late 914 calipers.

--DD