I'd always heard that the MiG-37 was a totally mythical Cold War scare tactic cooked up by the American government itself (No joke, I actually heard that somewhere).
I saw a couple of grainy (and I mean REAL grainy) photos in a book once that were said to be of an actual MiG-37. The outline of the shape in the photos was genearlly consistent with the shape of the bird in Italeri's kit, but it was so lacking in detail and fuzzy that I suspect it was nothing more than an intentionallty bad photo of a black paper cutout stuck to a window.
I had also heard that when the Soviet Union broke up, that the MiG bureau itself totally denied the existence of such an aircraft and that they never built or designed anything that remotely resembled what was in the Italeri kit.
On the matter of kits of it. Yes, Italeri did make it in 1/48 as well, but the 1/48 kit was not ever as easy to find as the 1/72 kit was.