The 600, 800 front ends were a bit beefier
than an N but not by much. Ford made bumper
weights for those. You could add up to four
80 lb weights to them = 320 lbs plus the
weight of the bumper itself. So I'm
thinking you could add 250? lbs to an N
with no ill effects. Now the bumpers were a
bit sturdier too than the N bumpers plus
part of a bumper/weight kit was a bracket
that hooked near the top of the bumper and
angled back to the rear of the axle to help
support all that weight on the bumper.
First photo is from the Ford parts manual
and shows the whole kit and kaboodle.
Ford continued to sell this kit till well
into the 1970s. I have that style bumper
with 2 weights on my 3000 along with the
rather rare original angle brackets.
It would not be difficult to make a set of
brackets to fit your N and bumper. Then I
would not hesitate to add 200+ lbs.
A couple of additional thoughts:
Ns carry some pretty heavy loaders on them.
Now the geometry of a bumper and weights is
a bit different than a loader but they
aren't nearly as heavy as a loader.
Also, I use this tractor mostly for mowing
and get Much less scuffing on the lawn
because of them.
Lastly, I use a boom pole on the 3 point
often and can lift a lot more with this
weight in the front.
Sorry this got so long...