I am sure that this question is a total newb

question but I will ask it anyway.
I am getting all the parts together to rebuild my 350 SBC. Had it bored to .020, will be putting this crane cam and hydraulic lifter on it. New springs, rocker arms. If I am not mistaken the pushrod length should be stock?? Are they all the same? Should I look for a certain type or brand?
thanks in advance