Your Dana 30 will last for some time depending on how heavy your right foot is. The Dana 35 will snap an axel..its not a question of will it but when.
33"s are about the most a Dana 35 can handle, when you throw 35 inch tires on its too much for the small axel shafts.
A Super 35 kit will help but thats thowing good money at a bad axel, the outter tubes are thin and prone to bending, a axel truss will help this but yet again your throwing good money at a bad axel.
Dont get me wrong the super 35 kit is good, and with your life time replacment on broken axel shafts, its not a bad deal if you want to go this route.
But if your all bent on running 35's without the problem of axel failure I would look in to finding a junkyard Dana 44 (the cheapest) or spend some more and go eith a 8.8 or a ford 9 inch. If your plans down the road include a V-8...a Dana 60 would be a good investment.