You probably have a seized up king pin. Pretty common. You should be able to figure out which one it is by jacking the front up (both wheels off the ground) and man-handling each wheel - attempting to move it back and forth as if steering it by hand. I'd recommend cleaning up the grease fitting real good then take a torch and apply heat to the bushing boss on the top and bottom of the knuckle - not too much, but enough to get it hot. Then you can work it back and forth some more and attempt to pump some grease in it and keep working it. Its not very likely your steering box is stuck. And by the way, that gear oil you put in there is all going to leak out in short order. It should be lubricated with a heavy grease like wheel bearing grease.

1950 4100 - unrestored and driven weekly for almost no reason at all.