I've spent the last couple days reading over the forum and I'm interested in building a 818c for a weekend car, autox, and maybe some track days. I've spent most of my life over the last 8 years racing autox and roadracing motorcycles. Upon researching if I thought I could tackle a 818C build in the garage it came to me of how come no one mentions or has built a K24 with a K20a head and put it in a 818? I raced S2000s for most of my autox career and after owning 4 of them I'm blown away by how reliable and easy to work on everything honda. Also hondas aftermarket is very broad. A K24 with a K20a head is easily a 500whp+ car and I've seen build sheet of almost 1000whp from a build that had a stock ported K20 head. The parts are available and also cheap.

The K24/K20 is about 275/300 LBS which is what I was finding the WRX STI motor weights.

Problems:
who makes a Adapter plate/flywheel?
Is there room for the motor? (K24 is 26" high, 20" long, and 16" deep)
How big is a EJ207 (that's the 2007 WRX STI motor right?)

Wiring should be easy because the K24 is often used as a swap to several cars so the aftermarket makes harnesses and other parts needed. My problem with the WRX motor is I've had a few people blow them up around 400whp which is a far cry from the reliability you would get with simply going to a honda motor.

LS3 would be nasty but I don't forsee that fitting.