Country boy is right on the money.
Yopu can get away with a cheap body lift of 3-4 inches. But with the shape of the wheel wells ont eh 97 blazers, you wouldnt be able to clear much more than a 33 x 12.50 i would think. You would alo show almost all of the center frame like Countryboy said.
A suspension lift would be the way to go. But since the truckis IFS (Independent front suspension) you will be spending well over $1000 for a 3-6 inch lift. And some of the lifts require that you cut off one of the front differential mounts. That makes the kit permanent. Once that mount is cut off, you cannot put it back to stock.
You will also have to keep a good eye on u-joints with a blazer like that. with the fairly short wheel base, if you lift it 6 inches or more it will go thru u-joints pretty quick. Also, with the bigger tires you will go thru front wheel bearings, ball joints, tie rod endes, idler arms, and pitman arms much quickler. It is all the price you pay to play.
Any questions, PM me.
Shoot'em close. Less to pick.
They might get my guns, but they'll get the bullets first !