Chevy Guru's help please

[Buffalo]

I have a 84 K5 Blazer with a new alternator, battery, and starter, I replaced the batt cables and still no charging.. I have power to the back of the alternator and all the wires and fused links coming off the starter but when i put a screw driver it is not magnetized.. please help. i have been at this for 4 days now and still nothing. It has to be something stupid im just overlooking. Any advice will be greatly appreciated!