Final two pics. 1) Primed, painted, and mounted in place. 2) Ground level view. With the shorter height on the second mockup, it extends halfway down the upper bumper opening. I thought it would fill the whole opening based on my test fit. I imagine that'll scoop up more than enough air as-is, but I could always extend a rubber flap down a bit lower if needed to catch more. I assume the stock setup works largely by suction, being a low pressure source of air, so at the very least this will flow as much as before since the snorkel's original opening is still there and has been supplemented along the bottom.
I ended up not using the intercooler bolt hole on the side that it lines up with, as everything feels rock solid.
While I had the headlight out, I figured I would try repositioning the high beam on that side, since it doesn't quite line up flush with the bumper, as seen in the first pic. No luck. Between the three mounting points and the tab at the bottom, there doesn't seem to be much wiggle room. Oh well, something in the frame or bumper cover must have gotten warped over the past 20 years.
I also tested all the bulbs as I was putting things back together and noticed that the driving light on that side doesn't work. I'm guessing it's been out all along and just doesn't have a failure indicator on the gauge cluster like many of the other lights. Has anyone replaced one of those bulbs and remember the part #? The best I can figure is it's a W5W 12V 5W bulb, but lots of very dissimilar bulbs also fall under that classification. Other markings on it include 7G KOIT E4.
'94 SC400: Goodkat ... "It's not something people hear about. Falls on deaf ears mostly. This particular one has been over twenty years in the making."