I have an 86 k10 w/ the four speed (granny gear), dont know what the proper name is for this tranny but anyway, my pedal pressure sucks! The clutch is not completly engaging so shifting is very strenuous and dont even think about going from nuetral to reverse or its grind time. I tightened the two bolts securing the clutch master cylinder to the firewall and that helpede somewhat. I have replaced the clutch, throwout bearing, flywheel, etc. already and I think the clutch master cylinder needs replaced.  I unbolted it and saw that the clutch pedal goes through the firewall and the rod(?) goes into the back of the master cylinder.  how hard is it to replace it? I pulled a little on the rod going to the pedal and it doesnt seem to pull out too easily out of the master cylinder. Do I need any special tools. Any help would be appreciated.

you probably have a SM465, check out www.67-72chevytrucks.com
they have a 73-87 truck forum where you can find almost anything you want to know.. just join and ask.  someone will can help you.