Some of the car companies (Ford specifically) moved their cams around by changing the crank and cam gears and not the cam. 1970 429 Ford cam gears when used on 75 or up 460's turn trucks that won't spin the tires on wet grass into trucks that will smoke the tires on any kind of pavement. That kind of retarded camshaft also effects gas mileage in the worst kind of ways. Sold many many earlier style timing sets to Ford car and truck owners after explaining the difference to them and never had a complaint from any of them.