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You’ve got a Gm corporate 12 bolt rear and a 6 lug Dana 44 front. Neither of which are the strongest or weakest axles out there. What you have will likely survive in mostly street use. If you want more strength than you will want to swap to 8 luggers. A GM 14 bolt full floating rear from a 73-87 1 ton 4x4 single rear wheel truck will bolt into your truck with the exception of 1 shock mount, and I’m pretty sure you will need a conversion ujoint. Also it will take a little work to get your E brakes working but not the end of the world. I’ve got one in My 72 K20. In the 67-72 trucks there was no 1 ton 4x4, 3/4 ton was top dog. It had an 8 lug Dana 44 which is marginally stronger than the 1/2 ton version. It you want more strength in the front than a Dana 60 from a 77-87 1 ton 4x4 (91 for crew cab 1 ton 4x4 and cab and chassis 4x4) is in order. The front Dana 60 is pure beef, with king pins, pretty big brakes and big hubs. They are getting harder to find but are still out there. I’ve got one about ready to drop into my K20. Whatever you do don’t scrap your existing axles. They are still valuable to someone wanting to keep there K10 original. Does your existing front have disk brakes? It has 70-72 style hubs but looks like it may have drum brakes hard to tell. 67-69 will have drum brakes with a close knuckle, 70 is open knuckle drum brakes, 71-72 is open knuckle disk brakes.
Also that red lock out dial is 70 only and pretty uncommon. Don’t loose it!