My 1990 E350 has 235 85 R 16 size tires.
6890
E4od
31by 10.5
Your tire dealer can help you with that.
You can lower it with the help of a mechanic. You can take it out and then place it onto the empty part.
P245/65r17 105s
1991 e 350 diesel 7.3 has 190 hp
225-60.16
P185/75R14
To remove the front tire from a Ford E350, first, ensure the vehicle is parked on a flat surface and secure it with wheel chocks. Loosen the lug nuts slightly while the tire is still on the ground, then raise the vehicle using a jack and secure it with jack stands. Finally, fully remove the lug nuts and take off the tire. Always refer to the vehicle’s manual for specific instructions and safety precautions.
Just use the suggested R15
http://wiki.answers.com/Q/Where_can_you_find_the_wiring_diagram_for_a_1982_ford_e3501982 ford e350