I have several of the SunStar Mach 1s...they are excellent for the price ($15 each when new), but they have a few flaws. The front and rear grill areas look a little "off" but a little judicious use of some model paint and it fixes them right up. Plus the tires look a wee-bit fake: no letters or other markings.
The Auto-Art model is much more detailed (and way, way more expensive! I think over $100 at time when new), but still has some flaws, but different ones than the SunStar.
And of course they both have the same, major flaw: They only put 351's in them!
I also have several versions of the Ertl 71-73 Mustangs, including the "Eleanor" version. The "Eleanor' is fairly accurate, but all the other Ertl variations are WILDLY innacurate.
One of them even has heater vents at the rear of the hood!
But they were cheap too...around $20 each when new.