They already make M18 Hellcat tanks, which it was based on. And wasn’t that vehicle heavily utilized in wartime?
They saw action in Korea, at least during the first year or so. I’m not sure if they made it into WWII.
Academy released a version of their M18 with M39 conversion in Europe some time ago according to Scalemates. But unfortunately it was never released here in the US. I could sure use one in my collection.
Legend did a resin conversion set but it is discontinued as far as I recall.
The noises about the Academy M39 were not encouraging. I toyed with kitbashing one since it’s all flat plates…
I’d rather have a mediocre one in injection plastic than none at all. People gripe about the Academy M18 as well, but mine looks close enough for government work on my shelf. 
I believe the M39 was also used by the West German Army, before they were officially stood up, for mech infantry training. I’m not sure how long after they were stood up that the M39 was used.
Edit: they were used until 1960 when they were replaced by the HS.30 Lang due to a lack of spares.
Damon.