What rubber boot? I believe you are talking about a rubber boot that goes around the clutch fork where it comes out of the bellhousing?? If so, from what I've always seen, the T-5 Mustangs do not have this rubber boot. It has an "inspection plate" that covers it.. it's a steel piece that bolts to the Bell and keeps the clutch fork covered...
You see it at the right side of the picture.. the black cover...