If I've done my research correctly you don't need new lifters for the street cam. I would still recommend using brand new hydrolic lifters but if the ones you have in the motor are still in good shape, why not. For the Sport R/modded motor cam I'm going to call them pretty soon to find out what exactly we have to have.
About mechanical lifters(I hate'em) I have an old dodge pickup with mechanical lifters and it makes clicking noises like a diesel and I really didnt gain much in power. From the looks of it all of these cams should go in without much trouble, Kent cams makes these to basically just bolt up,if you don't consider the timing adjustments and all.