As usual Jim is right on target, both as to interchangeability and the use of historically correct parts. I might add the following, in case it would be of interest, from R. Blake Stevens' book on the BHP.
In 1966 FN issued a "List of Assemblies and Parts of F.N. Origin Which Can Be Considered as Interchangeable with the Same of Canadian [i.e., Inglis] Manufacture." According to FN's list, the safety is interchangeable as an assembly, although "minor adjustment may be required." The safety assembly consists of the safety, safety stud, safety pin, and safety spring.
FN's list covers interchangeability only up to 1966. At that time, FN noted that "subsequent modifications may entail certain alterations." However, subsequent modifications, if any, must have made little or no difference, since Jim advises that any HP safety should work.