I want to build a driver K10

[franken]

Most 73+ rear ends have a different (wider) spring spacing and different shock mount than the earlier trucks. In front, 71-87 (later in Suburbans, crewcabs and maybe blazers) are the same or close.
NP203s for a doubler are sort of hard to come by at least near me. Look into a range box using an NP231 (or others) planetary gear set, NP205 and later model NV4500 for the killer setup that includes a super low low range (plus 2 less low lows), and overdrive. Later NV4500s have 5.6 1st compared to the earlier ones w/ 6.3.