The below is based on my observations putting 1989 LX 5.0 front brakes on my 1989 4 cylinder Mustang:
On the front brakes, the front rotors on 87-93 V8 cars are 11 inch diameter while the 4 cylinder rotors are only 10 inches in diameter. That makes a huge difference in braking power, especially from the higher speeds that the V8 engine is capable of. Now for the rest of the news. Not only are the rotors different, but also the spindles, calipers, caliper locating pins, splash shields, flexible brake lines, and flexible brake line brackets. You either change all of it together, or none of it. Preferably you change the front brakes at the same time you do the front suspension, it will save you time. One last comment on the brakes is that the brake booster is different between the two cars, along with the two short little brake lines that go from the master cylinder down to the proportioning valve. The V8 brake booster is thicker, giving it more internal volume to respond better with a lower engine vacuum level.
On the front brakes, the front rotors on 87-93 V8 cars are 11 inch diameter while the 4 cylinder rotors are only 10 inches in diameter. That makes a huge difference in braking power, especially from the higher speeds that the V8 engine is capable of. Now for the rest of the news. Not only are the rotors different, but also the spindles, calipers, caliper locating pins, splash shields, flexible brake lines, and flexible brake line brackets. You either change all of it together, or none of it. Preferably you change the front brakes at the same time you do the front suspension, it will save you time. One last comment on the brakes is that the brake booster is different between the two cars, along with the two short little brake lines that go from the master cylinder down to the proportioning valve. The V8 brake booster is thicker, giving it more internal volume to respond better with a lower engine vacuum level.