You still are ahead ClarkM
and all the places these guy suggested and if you still have problems I have a guy that collects all Mossburg stuff and I am sure he has what you are looking for (I will try and find his telephone number) - the are not cheap though
PennDog
I thought it was a Win 52 at a distance.
There was no price tag.
When I asked, I thought they would say $1,000.
When they handed it to me, one guy said, "$100.... oh how about $50?" and I am still thinking it is a Win 52.
Then I had it in my hands and I saw it was a Mossberg and said, "OK, I'll do $50."
Later at home taking it apart and comparing it to taking Win 69 and Win 75 rifles apart, the Mossberg is very well built like a Win. Not the same design, but equal in sturdiness and number of machining steps.
I would pay $50 for any Rem 510, and they are cheap stamped pieces of sheet metal inside.