They are not the same, any car guy can tell the two apart. Hennessy adds performance upgrades, slaps on some decals and sells fast upgraded cars and trucks. If that's what your after, he offers a fine machine. They also call themselves a tuner shop. Saleen on the other hand takes a new car and creates a complete new automobile. Installs new body panels, parts, repaints, new interior, suspension, performance upgrades.
The Heritage Collection is far from a Tuner product. SLNN is a specialty car manufacturer that offers the complete package.