Captian,
6 degree caster blocks have just been released, not sure who has them in USA. You can find them on the TOP Japan website.
Otherwise, you could adjust caster by adding spacers under the suspension mounts.
More spacers under the front suspension mount = more caster .. but adds 'pro-dive' (less initial turn in).
More spacers under the rear suspension mount = less caster .. but adds 'anti-dive' (more initial turn in)