1991 Silverado Radio

Hi there. I've tried posting this on the car audio forum, but nobody seemed to know the answer, so hopefully someone here will have some specific experience with this problem. Someone I know is asking about how to install a new deck in their 1991 Silverado. Apparently he's heard numerous stories about how you're supposed to use the amp, how he should just get rid of the amp, even that he needs to obtain a new one from the salvage yard. Does someone have a definitive answer to this? I've done some searching and I can't seem to come up with a definite answer. Any help would be appreciated