Why not use the 4-link out of a Sunny B310? It even has the brackets, just need to weld them to the 1200 ute. It is quite heavy duty, they used the same on 1983 Silvia with the H190 diff.

Or better yet use the whole rear assembly out of the 1982-1983 silvia it fits under a ute as it is only 2" wider and has disc brakes.