my 1972 c10 used to gring going into first gear and the clutch had a very low release point. Now i cant get it to go into gear at all but it drive fine if i crank it while in gear, in all gears......pressure plate??, slave cylinder???

I would check the adjustment on the linkage you should have a mechanical linkage clutch on a '72 unless one or someone else converted it to hydrolic. Also check for slop in the linkage or worn out brushings if that all checks out. Inspect your throw out bearing and clutch fork assembly and fulcrum point.