Thanks Jack. I found info at
http://www.chuckschevytruckpages.com/73-87specs.html that indicates the newer trucks used a smaller ring gear, and a semi-floating design. I haven't picked up the truck yet, so maybe I will get lucky. Who knows, maybe the truck was ordered with an upgraded axle or something. Anyhow, I've got a very good start I think. I just checked out your site, that thing is looking GREAT!! Keep us posted...