what speaker size and brand work best for the dash and rear side speakers in an 89 iroc??

dash speakers are 4x6's the only thing you have to watch with these is the size of the magnet on the new speaker because most new speakers use bigger magnets that may not fit. the back speakers are 6x9's and the same thing applies with them but isnt as big of a problem because there is more space. as for what brand it is all a matter of opinion if you are looking for a cheap system pioneer isnt too bad if you dont mind spending some money Re has some amazing 6x9's i should know i have some lol but you would need an amp for them. if you have anymore questions about what brands or anything just p.m. me

For the front you cn use a 4" &1" plate speaker. You could also cut the dash to accept some 5 1/4" speakers also.

The rear can tak a 6.5" & 1" speaker or 8" sub if you want.