You can use whatever weight bullet you want. What you shouldn't do is shoot a steady diet of full-power 125gr loads through it. If that's what you want to carry, then there shouldn't be problem if you wanted to fire a cylinder or two every few months to maintain familiarity with it and shoot heavier or lighter loads on a regular basis.
Personally, I wouldn't go with the full-power 125gr loads because of muzzle blast. I'd rather go with the mid-range 125gr loads or even .38 Special FBI loads. I have a 3" 65 and it's usually loaded with Buffalo Bore .38 Special standard pressure 158gr LSWCHP. I also have some Speer .357 Magnum 135gr Short-Barrel GDHP that also shoot well in the gun.