The full size blazer has 5.25 in the kick panel and 4 x 10's in the rear.
235/75R15
If you still have the factory speakers installed, each door speaker is 6 1/2. Be careful removing the door panels though, they can be a pain in the arse! Hope this helps!
6x9 is the speaker size.
265/75R16
235/75/15 stock size
4x6 in the front dash
From the factory there is no tweeters in the speaker system.
Ft
6x8
2.8 or 4.3
235/75/15
The factory size is: 225/70-15