Pontiac engines by design have more bottom end torque than a Chevy. If it were my engine I wouldn't bother. That said, since getting at the timing chain is easier on a Pontiac vs the Chevy you can install it the 4degrees advanced. If you find the motor runs out of steam by 3500 rpm then pop the cover off and crank it back.

Just my opinion.

Many cams have 4 degrees of advance ground into them right out of the box, so if you install them in the "straight up" position they're already advanced four degrees. The only way to know for sure what you've got is to check it with a degree wheel.
As a general rule most engines will make the best average power with the cam advanced about four degrees but it's as you mentioned,,, advancing the cam usually adds to the bottom end and midrange but usually gives up a little on the top end. But as dcneric mentioned, the Pontiac engine is already pretty torquey so you might just loose top end and not gain much on the bottom end.
Advancing the cam usually works great on a low compression motor but if the engine has fairly high compression, advancing the cam will make it more prone to detonation. Piston to valve clearance can also be a problem but probably not in your case with a relatively stock engine.