Need Help Identifying

[Notyourplumber]

Picked this rifle up from a pawn shop in TX after going back and forth on it for about 8 months. Was sold as a Les Bauska .416 Rigby, my issue was there were no identifying markers on the rifle. I talked em down and purchased the rifle, got the stock off and found matching serial number “387” on the trigger, receiver and stock. Reciever has been cut to have some sort of optic mount installed. Bolt release does look like the BBK-02s and it does have the Mod 70 safety but no other markings that I can find. Pics below