Would a set of P255 / R70 16 tires and rims from a 2008 Ranger fit on my 1996 Ranger?

I guess that depends on the rangers. There is no way my current Rangers boots would fit on my old Splash. Need more info man! Try this tire size calculator:

http://www.miata.net/garage/tirecalc.html

If the bolt head pattern is the same and the overall hieght is the same they will probably work. I would ask a salvage yard that sells used wheels or go to and online tire store to see if the applications for your ranger and the newer Ranger are the same. Here is a sight that will tell you the height of different wheel tire combinations http://www.tiresafety.com/replacement.asp

The bolt patterns are the same 5x4.5. The rims will otherwise have a very simlar fit/offset. If anything the new rims would be larger as is the trend now a days so fitting over the brakes shouldn't be a problem.

This weems to be a rubber size question and the asker need to let us know what truck he had with what size original rubber. Then based on experience we could answer whether the rubber would fit without rub.