Retiring the '77 Highboy from active duty.
Picked up a 05 King Ranch crew cab PSD, totally loaded except for the most important option, a posi rear. Does anyone know of an aftermarket locking differential that's available? I searched the usual parts "warehouses" but nothing shows up. No harcore wheeling, but I tow my rigs on Colorado "roads", which can be impossible without maximum traction.
Any help is appreciated.

Im sure you could get a LS installed from your local ford dealer

Detroit locker,

Ford 10.25/10.5 1985-03 All Ratio, 1.50", 35 spline P/N 225SL-56A