why are you wanting to push your valvetrain to where you get valve float? that would be caused by the valve springs not being stiff enough, not your lifters. maybe you are thinking of lifter pump up . i agree that your cam will probably run out of steam before either happens. you will probably have no problem running it to 6500 rpm as long as your valvetrain has proper geometry. bent pushrods happen when something (usually a lifter) malfunctions. sounds like you got good pushrods so i think you will be fine. have fun but unless it's an all out race engine you probably don't need to wind it up super high.