I've no idea if this is a valid idea but: Would replacing the entire bogie assembly be easier than just replacing one arm?
Getting near a big tree and pulling it out with a come-along might work if there is no room to get a jack and some re-inforcement between the frame and the arm. Do they have trees in MT?
Then, if it is twisted, the spindle could be shimmed to get caster, camber, and toe close enough to be able to get someplace where permanent repairs could be effected.