Looks like Roy volunteered my services

Better pony up and see what I can do.
Guages are important. Not sure which "one guage" survived. Tach is needed, Oil pressure, engine temp, and ammeter are needed too. Fuel guage isn't life and death. Figure MINIMUM of $400 to fix 4 out of 5. (If one needing replacement is the tach) (inc. sending units/wiring, ect)
Brakes would be a MINIMUM of $250.
Steering hoses and hiem joints $350 MINIMUM
Grill & sheet metal (paint) IF you can find used or low cost aftermarket, MINIMUM $250
Lights, front and rear, aftermarket, $200
Misc. (Battery, ect) Figure a MINIMUM of $250,
So, about $1700 (plus a LOT of work) to get it into "good" condition.
$4200 would be a low price on a "good" 135, but at the high end of the price range for one in that condition. Fix all the described problems and you would have a $4500 to $5000 tractor, so anything over $3000 wouldn't be a "money maker".
You would have a good tractor. You WOULDN'T have a bargain.
Personally, I'd walk away. But SOMEONE will give him $4200 eventually.