Hummm...
That may have already been done.
I took a look at the fittings and I didn't see any of the bowing you'd expect with a larger diameter hose being clamped to too small of an outlet.
I'll double check.
Was both hoses being 5/8s something that was changed through the years, or is it just a remnent of my car's original 340 engine?
ie: did earlier Challengers all have 5/8 & 1/2 or did it vary by engine?