[zagrot]

it sounds much like an internitent bad connection. check the main power wire to the starter (B+ to starter). as for the stalling thing maybe there is another cause. is the clicking sound very loud and sharp? if so check the starter solenoid or starter relay (i think they are integrated in gmc starters). when you have starting problems do you do something to make the engine start such as move wires or such? more info would be helpful.