Ok thanks guys.
I bought the tailgate and put it on but it seems to be a 1/4" too wide. By "latches" I assume you are talking about the tailgate internals? I don't have the original tailgate so i don't have anything to swap into the 90 tailgate. I could get the catch pins off the 90 truck if that would make any difference.
I think I might shave the handle and create some kind of hidden deadbolt style latch.