first you have to remove the dash trim peice. its one peice that goes from the inside edge of your glove box all the way around the instrument panel. just find the best place to get in behind it and pry on it. if you're afraid to scratch it, wrap a rag around a screwdriver after you get it open a little bit. it has clips so find a spot where you think one will be and don't be afraid to fight it. just as you think you're pulling too hard, it'll come loose. the clips are made to pop off before the trim peice fails. there will probably be seven to ten clips to remove but after the first one they all come out with ease. you'll probably have to turn the key and put your shifter in low gear to manuveur the trim peice out of your way (assuming you have a column shift automatic).
now your internal dash is open and visible. there is a factory plastic mount that holds your stereo head unit in place. it has at least one alignment hole in it and probably 2-4 screws holding it in place. remove these screws and pull the entire head unit out of the dash. there is a factory clip-in harness that you need to remove. the clip should be facing up. depress that and pull the entire harness plug out. remove the antenna plug and you've successfully removed your stereo. now getting a new one in is a new chapter.
stock brand of tires for the 2000 chevy silverado 4x4 ext cab
All the speakers in a 1991 Chevy Silverado should be 4x6 if they are stock.
Yes they are interchangeable.
16x7
No, Chevy changed the wiring harness in 2003. and the way it is mounted, it can be made to work though.
285 hp
P245/75 R16 Chevy stock size
Should be the 700R4
it will probably be 3.73
probably a 350 small block
Stock speakers should be 4x6's
Generally, a stock silverado will have four speakers; two in the dashboard and two behind the seat.