Ok so......I own the 4x4 91' and my buddy's own the 2wd (red) 90' burb. They wanted to go 4x4 and I suggested they swap all the good stuff from the 90' into the 91'. They are both 3/4tons and both have 4l80's. His chasis has over 600k - yes that's 600,000mls on it and mine has 180k. His sheet metal looks good but isn't - mine is in good shape. I think this makes the most sense so we are going for it.