I used to have a 1973 K10 short box with 3.73 gears and posi in the rear and went all over the mountains of Colorado and Wyoming. Really did not have any real problems. Crossed steams (foot and a half), two tracks, hill climb, snow, Loved that truck. but no rock crawling. Now we just bought a 1987 K5 (first Blazer) 350, 700R4, and 3.08's with posi in the rear. I was afraid of the 3.08 gear because I did not want to give up any of the performance of the old 73 with 3.73. Went to this site http://www.angelfire.com/fl/procrastination/rear.html and calculated it out as; 750 to 1500 RPM's is what I mostly use to get over hard parts. 750 RPM -- 3.73 gear -- 2.52 TH350 first gear -- 31" tire == 7.358 MPH 750 RPM -- 3.08 gear -- 3.06 TH700R4 first gear -- 31" tire == 7.338 MPH So it looks like a WASH for cruising moutain trails. Any body have any info on this.