In a message dated 4/15/2016 9:03:56 A.M. Eastern Daylight Time,
lalofs@GMAIL.COM writes:

I am not  familiar with this part and it's hard to see the details from  the
picture.  Is it basically a Tee shaped steel piece with 4 holes in  it?  If
so, it could be fabricated without much trouble.  Do you  already have the
mirror image piece for the other  side?

More or less.. but you have to get the angle and hole spacing right and the
 holes have nuts welded to them. All '90-'91 passenger vans had these rear
shoulderbelts.  i have some OEM factory one FS from a '91 seven  passenger
GL if anyones interested.. WITH the seatbelts included..  (not just the
brackets, sorry)

the factory ones have the concealed reel.  Not a big fan of those
aftermarket GoWe$ty ones as the reel  sticks out and protrudes into the  interior of
the van..