When I read your title "tire and rim option" I immediately thought, is there really any other option than aluminum slots for our trucks? Then I read your post, you already have the aluminum slots, great minds think alike. How wide are the slotted rims you have? If they are 15 x 8 or 15 x 10, I would run some 33x12.50R15's with the 4" lift that you mentioned. In my mind' that would be the perfect look for a k10.
Just curious, Any idea what type of truck your 16" rims came off of? I've never seen a 16 x 5 6 lug rim on our trucks before.