86 Toyota truck starting problem

86 Toyota truck, 120,000 mikes, 22R engine, 4 spd. I've got a good battery, battery and starter connections. When failing, I can step on the clutch to the start position and hear the click of a switch (part of the clutch linkage?). The switch sometimes connects and I can start the engine but now it's unreliable. Is there an external or internal replacable switch on the transmission connecting the voltage to the start solenoid? What's it called or part number so I can do a part search? Thanks for your help. G 10/20/07