Why would you go to all the work of building a four link setup and then use a 8.75 rear end? If it is a drag car then put a Dana 60 in it. If it is a street car/road race car then use a Ford 9 inch. A four link install is going to require a ton of welding to the housing so the rearend needs to be stripped down anyway. At that point it only takes a little bit of work to cut the tubes to the proper length. Are you going to have a chassis shop install the four link or is this something you're going to tackle as a back yard project? You'll need a ton of tools, time and talent to do a four link conversion so narrowing the rearend will be the least of your worries.
