Why change it? The durations qbout right for the RPM,s with the 428 crank.
You don,t run the 428 crank more that 6000 (IMO) maybe less if you want
to keep it. It's a torque mtr man that is unless you have big bucks in the
lower end. In the ol days redline 7000 was for 427's, not 428's.
Good luck, Ron