The full size blazer has 5.25 in the kick panel and 4 x 10's in the rear.
235/75/15 stock size
A 3/8 Allen key.
2.8 or 4.3
The factory size is: 225/70-15
look at the info sticker inside drivers door. My 89 blazer came with 31x10.5x15 from the factory.
The correct factory tire size for a 1998 Jeep Wrangler is 225/75/15.
As far as I can tell the front and rear speakers are 6-3/4 in
there should be a factory tag on the drivers side door jamb giving factory recommended tire size.
Full size Blazer - 350 - .035 S-10 - 2.5L - .060 - 2.8L - .045 - 4.3L - .035