robbed power?
 

How much rear wheel horsepower will I gain by deleting the smog pump and air conditioning with a short belt?

You will not gain any noticeable HP by deleting the A/C and smog pump....The advantage of removing them is getting that weight off of the front of your car so that the weight transfers to the rear tires better.

At most maybe 1-2 HP for removing the smog pump, the A/C does not rob HP unlesss it is on.....If you deleted your power steering you would have a seat of the pants difference if you are willing to take it that far.

Later,

Diet tips
 

The A/C, complete, weighs around 50 pounds. The smog pump weighs 7 pounds.

Hardly worth the trouble and you'll need a new serpentine belt , too. Your call, of course.