It wasn't federal regs that really killed the AMX/3 (they did have an impact on escalating development costs), it was Ford selling the DeTomaso Pantera. AMC wasn't expecting to sell but a few (30 is probably the right number) a year, but when Ford started selling the Pantera, a very similar car, for several thousand less than AMC could sell the AMX/3 even at a break-even price (which is all they ever intended), the project was cancelled. They didn't think they could sell even 25-30 a year with competition from the much lower priced Pantera. They were probably right -- there wasn't a bit "supercar" market, still isn't. Ford had the advantage of not having to foot any of the development bill for the Pantera. DeTomaso had already done everything, they were just buying motors from Ford. Don't know which had the idea to offer the cars in the US through Ford dealers, but it certainly was a good marketing move for DeTomaso.
It was discovered that Bizzarini, the Italian firm that built the prototypes (there really were no production cars, only six hand built protos) assembled another 3-4 cars and I think they called them the "Sabre". These were assembled from left-over and hand fabricated parts. I haven't found anything on them yet...