Age may be a factor, I think this was a '90's kit. The sheet actually looked really good until I went to apply. Who knows? I too just did an old Revell P-40 and the sheet was completely cracked. That's why I went and bought the Hobby Craft (ebay), to rob the decals from. When I opened up the box, I was so impressed with the nice recessed panel lines and cockpit detail, I went ahead and built the Hobby Craft.
Oh, and as for the 'Stang, it's the cheap-o 1/48 Revell kit (got it at Wal-Mart for like $8). Ironiclly, those are the out-of-the-box decals and they were awsome! They applied smoothly and layed down fantasticlly. Aside from that, it was the first kit I'd done since I was a teen, and my first attempt at air brushing. Here's a better pic...