blackkite's first pic shows the 75mm cannon installation. The second pic is of a model kit. Do you know what kit it is? I would love to make a model of this plane if the kit wasn't too expensive. Stargazer's 3/4 view color plate is new to me.
My guess about the pic that looks like it's from a model is that it is a resin, not plastic, kit. There do seem to be a lot of parts, but they are numbered similar to what you would see for a scale model.
You are correct Rikugun did design other aircraft. I misspoke. What I meant to say was that it was the only aircraft that they actually built and flew.
IMHO you are looking at an actual subassembly breakdown for the real aircraft. For example, look at the structural connection points. I am no expert but have taken apart a few real airplanes.
From an archived version of alternatehistory.org.ua. Lists only a single source, but the source is in English so I do not know from where these drawings originate sadly. Especially sad is that this source (or collection of sources) often has redraws of original engineering drawings and appears to be pretty reliably based on primary sources.
強制冷却ファン : forced cooling fan, 発動機空気吸入口 : engine air intake, 潤滑油冷却器 : oli cooler, 空気入口 : air intake, 防火壁 : Fire wall
Engine ram air intake is located behind the force cooling fan, inside of the engine nacelle same as Raiden.