Al,
The truck for Sermis just might be the longest thread ever. The first bits of the truck made it to my class in November of 2008. It is still there. Mostly complete, but not all the way yet.
You are interested in the D60 castor angle for your build. I am not talking down to you. Just making sure we are on the same page.
Caster can best be described with a reference to bicycles. Think of the old Banana Bikes with forks a mile long. Huge caster, very stable but took a football field to turn and lots of effort. Then think of a BMX bicycle. Almost 0 caster, very quick to turn with no effort but almost no stability. As long as the front axle was in front of the handle bars it is positive caster.
If you were like me and stupid. You at least once tried riding with the handle bars and front fork reversed. That is negative caster and extremely unstable. Cars without power steering almost always had negative caster. The 1974 Dodge Duster for some reason is bouncing in my head as the last domestic vehicle with negative caster.
So, with power steering and big tires you want some positive caster for stability. As in above 2°. Too much though causes death wobble. Which was actually a problem on the long 7 series BMW and LS Lexus cars if tires and front bushings were worn. They were up near 12°.
The CUCV trucks, M1008, M1010, M1028 and M1031 all used the Dana 60 open knuckle front axle. The had the same specifications as a 1985 K30. Which was 8.0° plus or minus 1°.
However, that angle can change very fast when the rear of the truck goes down. If you are building a flexing suspension. Then a static caster of around 6° might be a good starting point.
This all make sense and answer your questions?
Remember if you didn't build it you can't call it yours.
6.2 powered M715, 5 M1009's, M416, 2 M101's, 2 M105's, 3 M35's, M1007 6.5 turbo Suburban project called Cowdog.