Fist check for any loose fuses, particularly the interior lights, horn, or cigarette lighter. One of those will be the memory circuit for the radio for its station presets and the clock. If the station presets are remaining in memory, the clock problem is internal to the radio. In that case get out your wallet! GM has built the Body Computer into the radio to prevent you from buying an aftermarket replacement. Without that radio you won't have cruise control or power windows. In an effort to prevent me from repairing the radio for you at very low cost, they will not sell radio service manuals after the '94 model year. You MUST have the radio removed by the dealer, ($), sent to their repair center, ($$$$$), and it must be reinstalled by the dealer and reprogrammed by them to your truck, ($). Expect a total repair bill of around $450.00. Got'cha. GM is very good about separating owners from their money after the sale. That is how they remain profitable when they are losing their repeat buyers.