Good question, but can't answer that one. Since your not getting much of a response, maybe consider contacting the roof rack company to check fitment. Or, one of the many roof rack mfg companies that specialize in off road racks - they must have encountered this question before. Maybe a Ford Bodyshop could help. Most folks don't put racks on their cabs and finding one that went from GEN1 to GEN 2 or vice versa would be the rare bird.
When looking for cargo/ladder racks I found there’s not really much out there. I found it much easier to just modify what I had. If I was in your shoes I would measure the trough width of your truck and measure the mounting of the new rack. If it’s close in size or a little over you may be able to cut the cross sections down and make it fly. Hope this helps. Otherwise you may look into a truck outfitter to do this, they may even have a plan of action from previous builds or whatever.