The RED one is a NICS engine. It is the earlier of the 2. And has less power.
The NICS has 2 inlet runners per cylinder, 1 of which has a butterfly that opens and closes depending on the requirements. These tend to jam, so that the engine is either terrific down low and crap up high, or crap down low and terrific up high.
The heads are different, but interchangeable (I know the inlet manifolds are not interchangeable).
That's my limit. Anyone else add or correct.