I have a 1998 Chevrolet Blazer LS 4x4 4 doors, and 4 6x9 speakers. I want to know how can i place the speakers on my Blazer, since the speakers it had were circular(i think 6.5")

 

You'll have to cutout and make custom baffles to mount them to and probably have to modify some of the sheet metal while you're at it. There's not much of anything you can do for the grills in the door panels though.

Why all the 6x9's? What's wrong with using a good 6.5" in each location?

 

6x9 speakers are the best. I think you need some cutting to make it fit.