A couple of thoughts.
Tires rubbing against the axle can be cause by a couple of things, too wide of tires, bent spindles and or worn king pin bushings.
I do not like to reverse my rims as it adds a lot more strain to the spindles having the tires so far out.
One thing you might consider is wider rims.
16" rims can be had in most sizes from 5" to at least 8".
On wider rims the offset is such that the center is moved outward allowing for wider tires.
You could look for some 5000 or 7000 rims which will be wider but have the same bolt hole pattern as your 3400.
You can also buy a pair of new 16" impliment rims in several widths - for less than a pair of cheap tri ribs.
For a loader tractor like yours I would consider something like 7 or 8"
Then you could run free/cheap 3/4 ton pickup tires without the rubbing problem.
Below is a photo of some big wide tires I got on a junky 4000 that I bought a few years ago.
They not need to be reversed and did not rub on the spindles.