I'm pretty sure that the center section of the ranger is offset to one side by a pretty large margin. I think that rules out a swap.
Also, like mike said, the ranger does not have the correct brackets for the four link setup. The mustang axle actually has the two upper controll arm mounts cast in the center section. That completely rules out a bolt up swap.
If you have an aftermarket rear suspension, like a torque arm or steeda 5 link, you could weld on the appropriate brackets and add new axle tubes to make everything fit.
With enough work, you can make anything fit, but this swap isn't a simple one.