84 GMC straight 6 repower

[burnin oil]

I missed the axle conversation but a little note about the Dodge D80. It is actually only a D80 pumpkin with D70 outers. If you look at the axle tubes you can see where they neck down at the ends. They also use the same axle shafts as the 70. Still it is one tough axle. The 3.55 gears work really well for all but the heaviest towing so I wouldn't worry there. My dads 2500 has the 4.10s and tends to pull in a little better milage empty or towing. That's not a fair comparison as mine is a 12v standard cab and his is a 24v ext cab short box. Both 4x4s with manual transmissions. If I was building the truck for some decent towing and not a lot of 70mph driving it would be 4.10s.