I am well aware of the D35 being a turd. I just got a sweet deal on a SBC YJ it still has the 35 in it. I am living in sicily at the moment and dont really have the means to get a hold of a JY 8.8 or any other rear-end for that matter. I plan on just leaving it open, getting some alloy shafts for it and crossing my fingers. All the threads I can find are just people saying the 35 is gonna break and they suck and blah, blah, blah. None of them are running a SBC and half of them probably have not broke a 35. My advice is carry some spare shafts and spider gears and go have fun. If it breaks, it breaks. I am forced to push mine to the limits with my situation.
as for the D30, your front end might last a little longer with the high pinion design. however your U joints and housing will be weak points (because the housing is the vacuum disconnect). I would just wheel em both and start saving your money, eventually you will need it for axles. FRONT and REAR.
Like I said before, I really dont have the means to go with anything else so I will upgrade shafts and take it easy on the skinny pedal until I get back to the states.