89 z28 with 5.7 want to get a cam but dont know what exactly to get what would be the best one to buy and what should the lift duration and brand be?

Why not call Comp Cams or Crane Cams and tell them what you are looking for, torque? horsepower? drivability? Do you have emissions testing? IS it for the street or track? Do you have accesories that require vacuum? You really need to knwo what YOU want the car to do before you can just throw out questions for people to answer. You are going to get everything from the mildest to the wildest and when it is all said and done it IS your money and your car. Talk to the pros who grind the cams then pick the cams you think will work and find liek a Camaro Forum on the internet and discuss it among the members. One person's choice is not the next person's choice. Educating yourself regarding cams is one way to keep from choosing the wrong cam simply because someone told you THIS ONE IS BEST! Maybe for him it is.....but how about for you? Draw up what you want and be real, nothing like 900 horsepower out of a stock engine with just a cam in it. And realize when you swap out a cam, you are going to affect other things like valve springs, rockers, are you replacing them? I belong to an Impala SS forum and there are a plethora of choices among the members which cam is best. Find a Camaro Forum, join and read and ask there. This is not what I call the best place to get your answer.