Alignment issue on lowered truck

[MAC71]

I have a friend that has a 72 c10 that he lowered 3 in with springs. He also rebuilt the front end, but with all stock parts. Before he took it to get aligned I told him to ask the shop to try to get as much positive caster as they could. He showed me the alignment sheet which showed 5 degrees of caster.

On my 71 C10 and 72 C20 I can only get about 1 degree and everything I have read states that 1-2 degrees is usually the max possible on these trucks.

On my friends 72 c10 with this much caster when he turned the wheels half way or more, such as pulling into a parking spot the front end would bind up and than the tires skip like the Ackerman angle was way off. He took the truck back to the alignment shop and they told him that they did nothing but changed the caster to about 1 degree. The tire skipping problem is now goon, but now the truck wonders on the highway.

Anyone have any idea how this truck could be aligned with 5 degrees of caster in the first place? Everything in the suspension is stock but the springs. And why the caster would cause the tire binding skipping problem? Also any good advice on how the effectively and coast effectively set up the front end of these trucks to give additional caster with out creating other problems?