Have you tried IH/Navistar....or Ebay
I "think" they are the same cooler (F series) from 86 to 94, there was an earlier model with 6 orings ours uses 4. That price is about right have you checked online dealers, do that once you get the correct info.
You can get the whole assembly here.....maybe they sell just the cooler without headers.......I have info on how to do the R&R ask anytime.
http://cgi.ebay.com/ebaymotors/Ford-6-9-7-3-Oil-Cooler_W0QQitemZ180215952345QQcmdZViewItem?hash=it em180215952345