I don't know this seller from hell or high water. Just something one might consider. If he's in fact truthful of his father passing he may know exactly zilch about an old 10-1/2" bell and a b-body 4 speed. I can tell you though, if my son, the geek extraordinaire (to me lol), were asked to get rid of my junk once I'm gone, he wouldn't have a clue on 90% it, what it fits, if it's good, has been modified, etc. I'm sure he'd just try to make it all disappear just as fast as he possibly could.
Then too, the seller could just be a no good, low down, turkey trotten..................
Blewbyu, Good luck on your resolution.
What are you putting the b-4 speed in?