Brian,
I am fairly sure, that all E-Series vans of the same era, 150, 250 and 350 are all the same "box" so all the sheet metal should swap, just like the trucks. Pre 92 the main changes were just in the grill and the location of the emblems, so there may be alignment dowel holes you may or may not need, but they are all the same physical shape. In the 92 + there were more changes made in the front fenders, hood and grill, so there are more era dependent.... so if you find the same year range, it should all bolt up. From the A-Pillar back on the 92+ should all be the same, it was just the nose they changed......