is it easy to swap a stocker for a hotcam like do i have to use shims and do other mods to make it work right or can i just drop her right in and do i have to put it back together run it for a while then take it back apart?

 

on a 400ex, you just drop it in. the only other thing you do is remove the spring and plunger from the head. everything else is good to go.