From what I have seen. The Dana 30 can handle up to 37's but I know a ton of people have 35's and don't have a problem. It's the Dana 35 rear that is gonna be your problem. It won't last long on 35's. people still run 35's on it but its very weak. Lots of people swap in a Ford 8.8 from a ford explorer. lot stronger then the Dana35, same lug patteren, and pretty damn close to the same width. Probably cheaper then beefing up the rear but i havent crunched the numbers yet. Let me see if I can find a link to something to beef them up like your asking though.
Edit: Here's a link. Chromoly shafts will beef it up.
Here is a Truss for the Dana35
Here's the link to our FAQ. Scroll down till you see 8.8 in bold red.