I got a Chevy 350 4 bolt main. I took the engine out and got it stripped down to the block. I gotta a question about the location of the cam hole. It is noticablly out of center of the casting. It is closer to the upper left of the block than from the center. Will this affect what kind of lift I can use on a performance cam? Would you recomend looking for a new block or could I still rebuild it? Would the left valvetrain get more lift than the right

this is a very common problem and if it is really bad off center then i would just get another block because it will never be the same

Most likely what you are seeing is some core shift in the block. I can't imagine the cam bore actually being drilled off center and having the engine actually run properly which I assume it did at one time. Core shift can be an issue when you try to machine the block such as cylinder boring. You may end up with thin areas in the cylinder.