Cool build CrazyDrei, I like your low-budget approach!
While 37 inch tires are indeed a lot of tire for 8.25" IFS front differential (or any 8-1/4" differential come to think of it) and CVs, my humble advice and an option that I haven't seen anyone mention is "carry a spare CV axle" and have the tools, supplies, knowledge and practice to do a trail swap-out if needed. The chance of having a complete CV failure to the point of making your rig no longer drive-able would be pretty small, and you'll probably never have to do it (it would be a PIA out on the trail), but if it comes down to it, its definetly an option.
Now if your front differential fails completely (I've never seen a documented example for the 8.25," pictures anyone?), that becomes a slightly more interesting problem, but it's still possible to get off the trail in 2wd if a little ingenuity (E.G.: trail hackery) is used...
I think the key with a tire this big on a rig this heavy, is be gentle with the go-pedal. Treat it like a sensitive friend that doesn't take criticism well.
For a rear axle that is better capable of handling those big meats (it would be more difficult to find then a replacement 8.5 ten-bolt, especially for a reasonable price, but they are out there) you might considering looking for a 6-lug 9.5" semi-floater 14-bolt out of a similar-year Suburban, Escalade or GMC Yukon, but make sure it has 4:10s and don't fall for the rear axle from a 1500HD pickup because it's setup for leaf-springs and not coils. Here's a link to an individual that did this:
http://z71tahoe-suburban.com/iboard/index.php?showtopic=34465 These rear axle assemblies are notoriously hard to find, but a great upgrade, as the ring-gear is one inch larger and the axles are 1.37 inches in diameter. Not quite a 14-bolt full-floater, but much better then the stock 10-bolt you currently have. You'll need a conversion u-joint to work with your stock driveshaft when installing this axle.
Another option, and one that would be worth considering, is the more commonly available rear axle from a Hummer H2... Supposedly, because of the H2s weird hybrid frame design which is some parts 1500 and 2500 if I understand correctly, the rear 5-link 14-bolt 9.5" axle will bolt into your Suburban, but please investigate this if you consider it because I've never personally done this particular swap. These axles came from the factory with 4.10:1 gears and a factory Eaton e-locker (electric locking differential) and can be had online for $600-$800 with free shipping. The problem with this swap is that it's 8-lug and the width of the axle is 3-4 inches wider then your current axle. The width isn't a problem, since it would allow you to just not run wheel spacers on the rear, but the lug-pattern is, because then you'd have to carry two-spares with you. Not a deal breaker, but annoying, especially for a matched set of wheels. They do make 6-to-8 lug conversion wheel spacers that are 2 inches wide that would work for the front if you wanted to run 8-lug wheels all-around, but being that those are 2-piece spacers, and that your running 37" tires, that would personally make me very nervous.
Of course, with any of these swaps, you'd need to find a matching 8.25" front diff (option code "GT5" for 4.10:1 gears on the RPO code sheet in the glove box) in the wrecking yard as well.
Lots of options to consider, some of which are affordable and some of which aren't, but at least there's options. :sombrero:
