Ryushi44

My parents have the same truck as me (2000 Sierra 2500 crew cab) and I'm trying to surprise them with a few repairs and upgrades. For parts half the truck is listed as 1999 and half is 2000. I have been trying to determine the specs on the original radio (1999 dash style). I want to replace their blown speakers but want to make sure the old deck can handle six new speakers plus the original tweeters or if I should just buy stock replacements. It's amazing how hard it is to find anything on these trucks.