http://www.forum.grailtone.com/viewtopic.php?f=3&t=15688
Basically use a Mark IV power section for reference for the III. Should be fairly easy especially as it's already done in Green Stripes but will check this for you: http://www.tubefreak.com/mk4-4.gif
From the Mark IV manual:
"Triode/Pentode Switch: This switch re-configures the circuitry for the two outer-end power tubes.
PENTODE increases power and punch and results in a harder clip. Use this setting for loud, live applications such as un-mic'ed blues or country gigs.
TRIODE lowers the power and softens and smooths the onset of clip. This makes it easier to get a rich singing sound full of sustain and harmonics but some headroom is scarified for this sweeter response."
