difference between a 742 and a 489?

440 with roughly 450hp. Its a stout motor as it propelled a steel bodied Duster to 11.80's at 112mph on slicks and 4.10's. Not my car but I heard it run in car before buying it.

I want to run 3.91's if possible. But would settle on 3.73's if I could find a good deal. Its going to be a street bruiser on the weekends, possibly see Mason Dixon from time to time.