91' or 92'Mustang

Mike's right, I forgot about that one. There would be very little difference between those model years. Ford almost put that brand out to pasture around that time, so there wasn't much investment in freshening up the brand then.

I don't know if a 90version would work or not. Are there reasons a kit may not be produced such as if there are neglible similarities to previous versions? How do manufacturers determine what kit years to produce anyway?

Revell had a '90 Mustang 5.0 LX Coupe and the '90 Mustang 5.0 Drag Racer.  Would a 1990 work for you?

AMT or MPC may, and that's a guess, have had one of it. It would be long out of production. It also may be a different year. Monogram had a Cobra in that body style, but it was a '93.