Look at the left side of the tang. Is there a shadow? Where the "Spain" was? PH usually removed the mark, don't know if other users of the SB action did. With the solid left sidewall and smooth rear bridge, the receiver was made for commercial sale.
Look at the magazine configuration internally, the underside of the receiver rails, and with a bit of experimentation, you should be able to determine which cartridges would work best, with minimum adjustment.
Any barrel intended for a large ring '98 could be fitted. Similarly, there should be no problem getting a stock.
Easiest way to refinish the trigger guard assembly would be to apply a coating.