The front 30 will be fine unless you get plum crazy with it. The rear 35 on the other hand will be the problem. If you plan on rock crawling or doing mud bogs, be prepared for failures. If you plan on daily driving it & doing some lite trails on the weekend, you should be fine. Just remember to take it easy. The Dana/AMC 35 was in no way intended to be stuft with air lockers & 33" tires.
I agree with what Thomas S said. If it's been beat on by the PO, you could be in for problems. One of the first things I look at on a Jeep is the under belly. If the TC skid plate is beat all to hell & dented up, you know its been wheeled.