Gearboxes can be changed/swapped no problems, just check & double check before final assembly. OR's (optional ratio) are in fact a mix of WR/CR ratio's. Cylinders are slightly different but can be interchanged, suspension on CR/XC looks the same, but WR is shorter with different valving. WR's are nice & easy to ride with smooth torquey power, a genuine CR is a bit toey with the very small internal rotor ignition and a XC is a basically a WR spec engine & chassis, with CR suspension. My XC430 has the first 4 gears from the CR & the last 2 from the WR, in effect an OR. Any or all are great bikes and generally easy to live with. Got a tidy '82 WR430 if you're looking.
Cheers,
K