We had four H's and an M on the farm I grew up on. I never heard of power steering on them, but we never bought one new either.
I think the steering linkage on the axle is standard. There is no room for it behind - there is a large assembly that holds the pivot behind the center of the axle, and braces that come from the back of it that are attached to the axle by the nuts you see under the axle either side of center.
See for example this one:
Finding the Family Farmall M
The wide front end on this photo above, the one posted by the OP, are the model we had on all our H's and the M. It bolts on with the heavy plate you see under the near corner of the OP's photo, and have a heavy casting that you can see in that photo extends down and holds the pivot shaft. The bracket in the center that controls the steering bolts on the bottom of the vertical shaft that mounts narrow front ends, ether single or dual models.
However, I do find this one, with a very different front end that has the links in the back:
Restored 1941 Farmall M Tractor for sale
I don't know the year, but that seat with the large coil spring is a late model.
Terry