Hello. I know that the stock 10 bolt axles are pretty weak. If you want a serious axle, most "crawlers" use the 1 ton Dana 60's and 70's. If you are looking for something that isn't as strong, but a lot stronger than the 10's, not to mention a LOT less expensive, the early to mid 70's 12 bolt axles will do just fine. You can use your current 6 bolt wheels and tires, which will instantly save $800 to $1500 in itself. The 12's can be re-inforced by welding gussets from your axle tubes to the gear housing to reduce flexing in extreme situations. I have seen, first hand, a 1973 1/2 ton Chevy pick up with 40" tires out wheel a 1 ton Chevy pick up with 44" tires. The 1/2 ton had gusseted axles, and towed the 1 ton back to town, because the axle tubes broke.
I am planning on installing Dana 44/14 bolt axles on my Blazer, simply because I can pick up a set for $300. Parts for the 3/4 tons are also more expensive than 12's. I have built pick ups in the past, and have had starter Blazer projects in the past, but was never able to finish them. I am very excited about this project. Time and money are my only roadblocks. I wish you the best of luck with your "girl" and hope you will keep us posted with the progress.