Hmmm… [puffs cheeks] Not a well known subject, this.

Fundamentally, the AM-37 was a development of the AM-35A which was intended for extended continuous high-perfomance operation. The motor was identical to the AM-35A except for the inter-cooler [described as a ‘spacer’ or ‘section-duct’ type] and the supercharger intake, the latter of which was larger at 285 mm (vs 275 mm). I can see no other fundamental differences between them.

What sort of technical detail are you after, I wonder? A PM might be the best course to pursue this matter is greater detail.