[slotard]

Regarding rake you're looking at tire diameter, it's radius that contributes to ride height so you'll get .71" rake.

How much space do you have between the top of your leaf and your frame rail? The thicker leaf pack and larger tube diameter of the C20 (vs C10) mean that you get more drop from an axle flip. If you're doing the flip anyway, removing the overloads won't do all that much (other than soften the ride).

I'd go for a basic 4L80E rather than a 2004R but the 2004R is an easier swap. On the other hand, if you won't be doing any towing/hauling I imagine it should be ok.