Hmmm, 275/70/17 is a bit unique tire size, most seem to be running 285/70/17 (33" tire) --- so will give you an answer based on the 33" size:
It all depends on length of your van.
(And assuming you are talking about an E-series Ford.)
Yep, fits no problem (from what most have reported.)
Fits -- but only if:
1) You have no rear frame-mounted hitch installed
2) The frame-mounted hitch you have installed is one of the variety that has an armature that is "V" shaped when looked at from below.
The added "V" kick rearwards at its center is *just* enough to allow the 33" tire to fit. The hitches that have a straight-across structure do not allow quite enough room for the tire to squeeze rearward of the axle.