the biggest cam lobe lift that can safely be handled by stock springs pre 87 are .500......and vortecs less than that.....but on the other hand.....if you are going to run a bigger cam with stock valvetrain i would use nothing bigger than a 216@.050 and a lift of about .450".....reason being, old springs tend to loose their strength with the test of time.....any decent bigger cam would be better with the matching springs.....much safer in the long run....no use putting all you time in a cam swap and then breaking the springs a short time later casue usually when a spring breaks it will also take a lobe out with it......I have seen bigger cams used on stock springs but IMO thats playin with fire.....take your time and do it right the first time.......you will be thankful in the end knowing that your entire valvetrain is matched and will withstand a beating when tested.....hope this helps.