The D44 and D50 gear sets are nearly the same size. Swapping just the D44 third member for the D50 will gain you nearly nothing, its the axle shafts and joints that are the weak point.

I would have to disagree with Brute Ford on the superiority of the 9" over the 8.8". Stock vs stock, the 9" will break before the 8.8", then theres the matter of an EXTREMELY low pinion and no VSS provision. The 9" has a terribly designed pinion support system from the factory. If your putting any serious strain on on your drivetrain components you should invest in an aftermarket third member for the 9.

The axle retention of the 9" is a slight improvement over the 8.8", but its no full floater. The axle shaft can still break and leave the axle housing, taking the wheel and brake drum with it.