Thanks for the links, Turbo Zetec!
Looking at XR2i brought me to the US-Market Capri XR2, which had a Mazda B6T engine, whose ports look familiar...I wonder if my inlet is a modified aftermarket Miata piece?
I've already moved the idle valve ports, maybe I could just blank the throttle body outlet on the face of the inlet and cut in a new one at the top. I'd still eventually like a more svelte OEM inlet, but for now just moving the throttle body might keep it from going *CLANK* against the wings and valance every time I load the engine.

That Dunnell water rail looks like exactly what I need; the Retro-Ford looks like it leaves the thermostat up against the firewall and doesn't look like it has heater outlets.