2000 Pontiac Grand Prix GTP, 3.8L V6 Supercharger.
It my brothers car, and before it broke down it was over heating bad, and the car would shake. After looking into it; we found coolant in with the oil and found that the intake gaskets were shot so we replaced them, also the person who owned this car before my brother had cut out the thermostat and put just the housing backing to it.

When the tow-truck dropped it off at my house, it was trying to turn over but just would not kick over.

While we had the engine taken apart we replaced the following items. Battery, also cleaned the battery connections, spark plugs, oil filter, oil, intake gaskets, cleaned the air filter, and replaced the thermostat.

Now that we have it back together, and tried to start it, it just clicks once, and nothing else.
I am lost on this one…….

If it was the starter wouldn’t it still rotate……

The only thing I can think of is it is the wiring maybe, but I drought it

Any ideas???