I found a couple of pics of a product line I once had a hand on (early 90's)
http://twentywheels.com/view/15179-lk_leeboy_300b_roller_169_hours_since_in_nj.html
Underneath the front (steering/pivot) yoke on the roller is a tube running from front to rear
with a pin through both the yoke and frame tube.
There are two bolts underneath the cross tube that face upwards to hold the pin,
in line along the length , not indexed at 90deg that shorter shafts usually need.
It's a common wear area and major pain for the person to remove in the field when those
bolts had burred up the shaft.
I took note of where the bolts hit and when building up the front end assy, I measured and with felt tip marked the spots and just knocked a pair of good sized flats with the 4" grinder.
A couple of details tell me this isn't one of my assemblies, But the pic serves the purpose here.
In the diagonal view: Red arrow points to the shaft, green arrow sort of at the area where the bolts would be.
Strait view: There are a pair of braces welded underneath the the frame, half by two and a half (the exact dimensions sort fade from me now)
I'll have wait till my hands aren't burning from yardwork, to do up a sketch of the welding fixture and its use of flat spots and then indexing from them with the "T" bolt.
The damper ring was for turning the rear drums of the 400 series.
The1/2 wall would start to chatterand go to a howl in a few seconds with out it.
The guys before me had been propping a wooden 4x4, with a bucket of junk hanging from it for weight, against them to try damping the problem.