What you have there is an SVO Mustang front brake rotor setup.
You have yhour original Mustang spindles, but you are running rotors that came off an SVO Mustang or a Lincoln Mark 7 and also used on the Fox Saleen Mustangs. It's identical to the Mustang OEM rotor except that it has 5-lugs.
The ranger rotors are used when dealing with the 79=86 Mustangs and the 87+ 4-banger Mustangs with the 10"front brake setup. The 87+ cars with the 11" brake setup use the Mark 7/SVO rotor.
Yes, you will need to change spindles to make the SN95 brake setup work. It's a lot of work, and not all that cheap. The GT's and V6's have the same identical front brake setups while the Cobra uses the same spindles but with a larger rotor and caliper. Up to you to decide what level you want to go with.
For parts you will need to get spindles, rotors, caliipers, brake lines, brake line adapter, spacers for the ball joints, a bumpsteer kit (may or may not need this) and then get it aligned afterwards. Then you will need to change your master cylinder and install an aftermarket prop valve.
AFTERMARKET 03 Cobra wheels may fit better, but unsure which brands work and which don't. It would be expensive to experiment so i woulnd't take the risk