1999 Gt Few Small Problems

Time for a new transponder ring and ignition cylinder? Stuff gets old.

My take.

That PATS has been disabled via tune. That's why the theft light stays on "all the time" because as far as the cluster is concerned the key has not been accepted.

It very well may be possible there are other problems with the PATS system hence why it was disabled in the first place.

As for the key minder. I think the door ajar switch is stuck open. It's a common problem in older Mustangs. Water gets in between the door panels and makes things stick. Take the inside panel off and spray some WD40 in the door ajar switch should fix it right up. The door ajar switch is located near the door claw.

Regarding any "missing" cluster lights. Turn the key on but do NOT crank. All of the cluster lights should light up for the "lamp test". That should answer the question about IF there's a bulb burned out or not. OBTW, it DOES happen. Or the prior owner may have removed the bulb in order to "fix" a different issue.

If pats has been disabled it will flash for a few minutes each startup then go off.

Don't fear the gear. With that said you need to keep future plans in mind. Do you want to up the power with n2o or a blower? Do you want to stay na.

Either way I'd do a 4.10 and run a taller tire if more mph is needed in the 1/4 mile.