I used to tow a 1500# camping trailer with my 90 on 3" and 30's, manual, 3.55's, fully loaded with wife and kid and stuff. Did fine, had to rap it out over Monarch pass, but, hey.
Now that it's worn out, I tow an M-416, loaded, with 4.11's and 33's. Not exactly a speed demon, and it blew a quart of oil going over Monarch, but it gets there.