The tough part will be finding DBM with top bolt release. They aren't made that way anymore, as far as I know.

Might be better off getting a Hog Hunter or Cabela's 12fv (both are top bolt release, blind mag) and then buying factory DBM bottom metal for top bolt release. I might be able to come up with a s/n for an older gun that came that way from the factory so you can get the parts you need.