Theoretically.. I'm sure the physics tells you you can do about any size and get it moving .. you'd just have to be gentle.. the general consesus is though.. stock AMC20? I think is no bigger then 35's without having to be real carefull.
35's is max even if you put money in you d30 and amc20. I swapped out my amc 20 for a nine inch and soon the d30 will be a d44 or d60 along with 35 spline axles and hopefully ill be going up to some 38's [img]images/graemlins/laugh.gif[/img]
I know of 4 people that have the amc 20 and dana 30 setup and do some serious offroading. They are all running 36x12.50.15 tsl sxs and have little to no problems. I will say that all of the aftermarket companies state that 35" is pretty much the limit on this setup though. I bought 36's and I am gonna run them.
Take a look at 4 Wheel and Off-Road for their Ultimate Adventure. They had a 35" minimum tire size this year. Several Jeeps had the D30 front end and didn't break. They seemed to run some pretty serious trails.
The magazine article has the specs on all the vehicles.