Probably normal. At idle the alternator is not putting out all that much while the lights and blower tend to draw quite a bit... seems like most of these alternators are 35-45 amp... so they just dribble power at idle.
Do you have anything else on at the same time as the fan and lights? Do you have the stock alternator? Do you have a volt gauge? What does it read when you rev it up? When mine started this, my voltage regulator was going bad. I would make sure you are not getting addittional voltage from the alternator.
First things first-
If you have a multimeter check voltage coming directly out of the alternator at idle. Tell us what it is.
Next step would be to replace your voltage regulator (is '82 external?), and replace your alt. brushes. Not very expensive and not hard or time consuming to do, and unless its been done recently, probably needs it anyway. See where you are then. Also check all your connections, and the grounds. To a certain degree, its normal for your lights to get brighter, etc when you hit the gas, but especially if this has just started, it could be a sign of short brushes, or a volt reg thats going bad.
WHat you describe is normal.Most all cruisers do it to some extent. Check the belt tension and clean all contacts. At idle with all the stuff on you should be at or just below the mid line on the amp gauge.
You can also check the earth lead where it bolts onto the motor.I found mine was a bit loose and the lead was corroded and needed replacement.Spraying crc/wd40 directly on to the fuse box of an older car can decrease the resistance in the electrical system.