WELL THE BEST THING FOR YOU TO DO TO UNDER STAND IS TO GO TO THE AUTO PART STORE AND LOOK AT A BOOK FOR YOUR MAKE MODEL AND YEAR. THERE CALLED HAYES BOOKS THERE NOT AS GOOD AS A MITCHELL BUT IT WILL WORK
there no such thing,you must be shopping at autozone or kragens if they sold you one.the blazer has a crank sensor if dis ignition or a ignition module in the distributor if it has a distributor