They are all crap. They are very stiff vinal, the heat warps them after a few years. My PO put one on my 72, it did the same thing you describe. They are just a band-aid, but at only 50% of a new dash pad price, they are tough to pass up sometimes.
When I bought my 70 Mach 1, it had a cover on the dash. It looked pretty good except it just didn't look right around the center A/C vent. It looked a little crooked. I bought a Dashes Direct orignal ford tooling dash pad from Virginia Mustangs. There was some problem with the fit around the intrument panel. I think if you take your time with glueing the cover on your orignal dash it should work OK unless you are fixing up a show car. I deafently wouldn't buy a repo dash. The orignal ford tooling dash is OK but you have to work with it, it doesn't bolt right in. If you have the money the orignal dash pad $450.00 would be the way to go. I bought one for a prior Mustang I had and it fit with no problems.
I have had a good experience with it. I got it from Mustangs Plus. The fit is very good, and it went on easily. The dash needs a little painting since it is being changed from brown to black. It was also much, much cheaper than the replacement. IF you have the money, I recommend the replacement, but at 500 dollars, it was out of my budget.
I have one in my '69 sportsroof. I was actually pleased with the quality, considering it's $65 vs. $300 for the re-tooled ones, and 2 arms and a leg for an original.
Mine's about a year old and has held up well so far through the 100+ degree days of a Sacramento summer, but it's spent it's whole life so far in the garage, not in the direct sunlight (I think it's seen direct sunlight for a total of 10 miles right now).