6 1/2s in doors, and 5x7/6x8s in the back, but the back ones are sketchy the way they load like in reverse. In my 92 XLT how it was. I assume it is the same. call crutchfield, they will tell you EXACTLY what WILL fit. there is a depth issue in the doors if you have power windows.
I believe (like 5 years ago) I got JBL 5x7s for the back, and the shallow mount infinity reference 6.5s for doors.
ps. 98 is easily rounded to 100

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99 Blazer LT. Yellow Top. Big 3. Infinity Kappa Speakers All Around. Jensen CD/DVD flip out. 2 Infinity Kappa Perfect 12DVQs powered by a Alpine PDX600.1 (in one custom box, building a FG box)
Site here says 5 1/4s in doors and 6x8s in back. but 5x7 is the same as a 6x8 i believe? dont know why. I dunno, but i KNOOOWWWW i fit 6.5s easily in the doors. I would definatly check this. I dont know why there is so much confusion, but you are right, there definatly is.
https://www.the12volt.com/installbay/detail.asp?info=alarm&year=1996&make=Ford&model=F%20Series&ID=17811&type=Stereo-------------
99 Blazer LT. Yellow Top. Big 3. Infinity Kappa Speakers All Around. Jensen CD/DVD flip out. 2 Infinity Kappa Perfect 12DVQs powered by a Alpine PDX600.1 (in one custom box, building a FG box)
Wow, thanks to all for the research and great info! Now I can go shopping and get the correct sizes. After looking at the stock speaker grill, clearance between the back of the grill and the front of the speaker could be an issue. Unless I get out the Dremel and sorta cut out enough of an opening to accomodate them...if I can't find shallow mounts. We are kinda limited here in AK.
