If you plan on swapping to SRW hubs I thought you could just swap to the internal style locking hub at the same time... If so there's a guy selling a pair of Chevy SRW hubs on Pirate right now with the rotors and all the bearings, races, etc included.
The wheel bearing hub assemblies are unique in regards to being setup for external or internal locking hubs. You can't simply swap the locking hubs themselves between external or internal style. So yes, if you swap in SRW hubs that are made for internal style locking hubs then the above is true.
Dodge did start using internal style locking hubs around '90 or '91 up until around '93 when they switched to the new body style with a unit bearing front axle (i.e. no locking hubs).