I am doing the 14 bolt conversion on my 1951 GMC 253-22, I acquired a 1976 C&C axle for $100. I am going to utilize the drum brake conversion to single wheel 13x3.5, I am in the process of having two spacers made for the backing plate. I found, through Summit, Currie spring pads, 2 inch width, 3 inch tube size, also having them machined to 3.375. The hardest part so far has been the removal of the old spring pads. The rear came with 3.73 gears but unfortunately water got inside and ruined the gears, so I am converting to 4.10. Also the spider gear cross snapped an end off and took out the carrier, so all new parts inside.
I will provide an update once I have the spacers, to see how everything is going to line up. The biggest problem I have with the HO72, are the brakes, the real reason for the 14 bolt swap, the rear is in really good shape otherwise.
My only concern about the 4.10 gears will be the loss of power from 5.13 gears but will like freeway speeds better. The current engine is a 248 bored .060 over.