Building 383 Help

We took a .509 PurpleShaft out of an otherwise stock, original paint survivor '69 Road Runner and the owner was ecstatic!!! With a set of Pypes Race Flow or Jones Max-Flow 2.5" mufflers, etc.,they sound awesome and have zero driveability issues like some of these "extreme" or "voodoo" grinds might.
So you recommend a .509 purple for a street but drivable car, or were you saying you replaced the 509 with the split? Thanks.