Using the RPM calculator at Randy's Ring & Pinion's website as a guide,
I'd say 4.56's are the bare minimum.

With 38.5" tires at 60mph, it would put your engine speed at 1671rpm in
overdrive. That's close to my engine speed with 3.73's and 31" tires
(1698rpm) so you should be good with the 4.56's.

~jp