Tire sizes 1990 ford e350?
My 1990 E350 has 235 85 R 16 size tires.
Every Ford product will have a sticker on a door jamb / pillar, or on a door itself, that specifies the approved tire sizes and tire pressure for the specific vehicle. The stickers appear to be in a variety of places - even within a particular year & model. Look in these places on your car to find it.