When you get to that point, I would suggest you find an auto/4-speed cross member. Should not be that hard to find. Many automatic cars being sold as parts. If you don’t have any luck, I will measure and let you know then.
The 1962 4-speed was NOT offered until April of 1962, just a couple of months before the assembly line converted over to make 1963’s. Probably of finding a 1962 F-85 bell housing with the 3-speed and 4-speed capability is not very good, but don’t give up!