The RCD has a known weakness on 98-00 trucks. The RCD kit comes with an axle spacer to prevent over-extension of the CVs, but because of the design of the hubs you can't use the spacer on the 98-00 model trucks, and in turn increasing the chances of breaking a CV. I'd either ditch the locker, spend $500-$700 to convert to the newer live axle design, or be easier on the truck.
Keep in mind if you were to convert to a live axle you'd still be stuck with the weak ranger IFS, you'd just slightly slim your chances of breakage. Also you lose your manual hubs so if you were to snap a CV you have to way to disengage it.
2003 Ranger Regular cab 5-Speed 4x4
D30 SAS | KING Coilovers | Deaver f31s | 4.88s | Detroit TrueTrac | Eaton E-Locker | 35" MTZs | 1354m | RE Long Arms | Currie AntiRock