I've been meaning to start a build log on here for a while. I maintain a build log on a forum I administer, AusRotary.com, and this will largely mirror what I wrote there.
By way of introduction, I have owned my series 3 RX-7 since 1999. I'm the large owner and have seen through a lot. It was largely standard for many years, with only upgraded suspension, exhaust and an extensively modified standard Nikki carburettor. I managed to get 119rwhp @7800rpm out of the standard 12A, which is truly incredible given it had standard ports. Those tall primary ports on the series 3 really do help once you get the engine breathing properly. A decent diff ratio like 4.44 and you have a fun car to drive.
Unfortunately in around 2005 my trusty old 12A developed a water seal leak after overheating (blocked radiator). Proper rebuilds were not possible back then since we had all just run out of new 12A housings and pretty much all of the second hand ones had severely worn chrome - even the apparently healthy engines. This was just an inherent weakness in 12A housings. Nowadays lots of people are able to machine down and restamp 13B housings as 12A but not back then.
So I bought a halfcut from a JDM series 5 halfcut and set to work transplanting the engine. I kept it in NA form and using an intake manifold adapter, ran the same s3 12A manifold and modified Nikki carb. Since the 13BT has lower compression rotors and the exhaust I fitted was more suited to a bridgeport, this engine made less power than the 12A, but it had a lot more mid-range torque.
In 2008 I moved house and although I updated my address with VicRoads (our local road transport authority in Victoria), the online tool didn't work and I never got my rego renewal reminder. By the time I figured out it was too late and my car was unregistered. I tried to re-register, then picked up the new engine number for the 13B (even though it all looked stock), ran it through the database and saw it was a turbo block, then said I need engineer approval as the engine was rated at 147kw instead of the factory 85kw.

Basically I was up a creek. Marriage, house, renovations and 3 kids later and the car is still off the road, but I am now in the process of getting it back together.
Here is the ride now:
And now for what's in store...