BIG UPDATE for those of you still following this thread.
Took the leap and dropped ~$2500 on the ABC clutch kit. Balled out and got the triple plate clutch option. Really impressed with the quality of everything, the adapter plate and flywheel are very nicely machined. Throwout bearing as well. Obviously the tilton clutch assembly is perfect, as to be expected from a company with such a good reputation in the racing industry.
Flywheel weighs in at 12.6lbs, clutch assembly around 7. Thats about the weight of a stock sr flywheel on its own, and with the much tighter center of mass it should rev nice and quick. Hopefully the triple metallic discs are driveable on the street.
fitment
Fitment on the adapter plate was excellent. Lined up perfectly with my block, hardware is nice. Only one of the bolts was unable to be tightened all the way because the adapter plate interferes with getting a socket or a wrench on. Nothing a little clearancing wouldnt fix.
There are dowels on the adapter plate on the transmission side. Very nice touch and very much appreciated to align the transmission right the first time. Fitment again was perfect. There are only 7 bolts that hold the transmission to the sr20, which im a little skeptical of, but the bellhousing only has 9 holes so i dont see it ever causing an issue.
The bellhousing will need to be machined or cut for the starter unfortunately. Shouldnt need to be cut by much, in fact it may only need to be clearanced a bit. Ill look into this more when my actual engine is finished and I can get the flywheel on.
the good stuff!
The transmission fits in the s13 tunnel like a glove. Seriously. Its like the thing was made for the damn car. Im actually still a little bit surprised by it. No clearancing needed anywhere. Theres miles of space from side to side (looking at you cd009), and from what i can tell it gets a little tight on top but nothing crazy. It sits pretty comfortably above the frame rails. Ran a broomstick across the rails and the only thing that hit was the drain plug, which was only on a thread or two. Everything else is about an inch above the rails.
The holes for transmission mounts on the transmission line up pretty perfectly with the holes on the chassis. Ill try to get something rudimentary fabbed up to see how it looks, but in theory it should be very easy to get a strong mount put in there.
Overall, Im extremely happy with my choice to go this route. A bit expensive, a bit undocumented, but really a fantastic choice for anyone with an sr, or a jz or rb for that matter that need to hold more power. I see less difficulty and minimal additional cost compared to a cd series transmission. Let me know what you guys think and ill keep updating as I get things like the driveshaft, shifter, starter, and trans mount done.