Need help on 8.75 rear end.

Just got off the phone with Dr Diff and Randy's Ring & Pinion and Drive Train Specialist, just like i mentioned I'm wanting to go to the 3.91 gear ratio. They do not make new stock 3.91, it stops at 3.73 unless you can get NOS from a Chrysler dealership parts counter or find a van or old truck that may have the unit still in it from where Chrysler put them in OEM . Please go back to my post and you will see that I mentioned that all I am finding for the 741 is 3.73
They are not a weak link and I never had a problem with them. And never mention that they were a weak link. There weak link is that they don't offer any lower gears than 3.73 new. That is why I asked the question. If I had all the 742 minus a case would it go into the 741 case. Simple yes / no and why. or what would i have to do as far as machining it.