Well if you're getting that high, whether you use lift blocks like that or just massively-arched springs, unless you got a real good panhard bar that axle is gonna feel scary every time you take a corner even at low speeds (well with the blocks it may simply break off and depart from the truck). If you do springs you don't really need the trailing arms, but with a lift like that you do need them, and he did install them, it's just that I feel their attachment points are poorly chosen and the size (and therefore strength) ain't proper for the application. But if he nicely overbuilt the blocks setup, moved the trailing arms down to the axle and way back on the frame, and lost the mile-long U-bolts in favor of two short pairs (per side, so total of 8 U-bolts) or even ditched the top U-bolts completely in favor of some good thick plate under and over the springs and regular hex-bolts (grade 10 tho) it can be made safe for driving on the road. Will it be good for the trails, hell no, but on the pavement and in a mud pit where suspension articulation is not much needed he will be alright. Again tho, this would require seriously overbuilding his current setup... As for the steering linkage, that's just downright scary, and needs totally redesigned, maybe even a hydro-ram setup.
Oh, and that Chevy, well, at least they didn't stack 2x4 wood as spacers...