the cam button will help if you do not have one you will need one . and you will have to set the end play no more than .004 but if you have a mark 6 you do not need one .it has a plate that keeps it from waking that has two srews to front of block behind the top timming gear. i used this cam in the mark 4 and 5 to but you have to use the mark 6 timming set .why do i use this type of cam? you do not have to worry a bout a positive stop. the plate keeps the cam from moving there is something to look at . not all bronzes are equal some of the bronzes is to soft and with hi volume pump will take them out fast.and the dist gear need to be check to make sure the dist gear is running in the milddle so the dist is not to hi or low this will eat the gear out to .this can be check with white grease or oil paint past type at the hobbie store if you have a msd with slip coller you can move it if not you will have to play with shims or put the dist in a lathe and make a cut on it were it sites on the intake. here is some thing to think about to if the cam bore is not true. bore up hill or down hill and not true to the crank bore on the block the cam will move in or out .with flat lifter type cam this is not a big deal the lifters are cut with some crown on them keeping the cam from moving