I'm not too sure why, I just bought the parts because they were cheap. Supposedly the guy acquired all these parts to go together, but sold his car before he finished putting the engine together.
The block seems to be standard with high comp smallport pistons.
The head is a 8 port non-distributor 7a head. He told me that this provided good air flow as opposed to the standard head.
I also got coil packs to run it and a motorbike throttle body setup with fuel rail.
He claims it was supposed to be a high revving NA engine setup with around 12.5:1 compression.