Husqvarna made the actions for the 51-L, but had nothing to do with the 50 and 51. They used FN actions and High Standard barrels.
If you do decide to restock a 50 or 51, be aware that the trigger is an unusual two piece design with the sear on the receiver and the trigger on the trigger guard. It is critically important that the distance between the two is the same as the original stock.
Or you could just replace the whole thing with a Timney.
