That was the case through '65 at least. And, if you find what has a 741 carrier in an 8-3/4" housing from an '62-'65 B with a /6, it will actually have an oddball 8-1/4" R&P, that was used only in those 4 years.
I think I would just rebuild the 8-1/4" if I were keeping the car and on a budget. For the much higehr $$ for the 8-3/4" path, it will add some resale value if the car is going to be sold anytime.