I rebuilt Starters and Alternators and made many mods for and type of tractor and vehicle from trucks (big and small) Limos(they need lotts of amprage) and Tractors.
The easyest way to upgrade you elect. system to handle your needs is naturally to change your alternator.Seeming you have a good battery (allways put the biggest battery that will fit)
What you need is a CS130 Alternator They came stock on your Chevy trucks. most of them are 110-130 amps.
You can get a used one from a junk yard but you need to know the mount type before you buy, Or you can go to an auto parts store and buy a new one. Request one for am 90 Buick Century.
It is a 110 amp alt. that has an straight up and down mount that will fit mostly any mount. It should handle all your needs. You also need the plug for the alt. you can cut one from a wrecked veh. any type will do as long as it is the same plug the diagram is simple if i remember off hand it is the white wire (bug wire) that will be going to your Battery positive for voltage sence and the brown wire for the ignition sence. This should do it I hope this helps you.