i can probably answer this right here and now..... and its an easy fix.

theres a bush on your steering column were it goes through the bulkhead. i bet you any money that if you knock this back flush to the bulkhead that it will sort the problem. this happened to me on my 4wd saph when i fitted a new steering column. i had my brakes, wheels, bottom arms etc checked and couldnt find the problem. i asked the ford mastertech at work and it was sorted it 10mins.

you can atleast try it and eliminate it...

good luck mate.

Riggie.