I'm really generalizing here, but there are two rough generations of cotterless three-piece square taper cranks & bottom brackets.

The earlier ones (1970s-1990s) were designed for road & touring bikes (although also used on early-generation MTBs), had straighter arms, and generally use 121-127 mm wide bottom bracket spindles.

The later ones (1990s-now) have arms that curve outward from the spindle to clear wider chainstays and provide better ankle clearance, and generally use 107-115 mm wide bottom bracket spindles.

As with all parts, variations abound. There is also the ISO vs JIS taper issue which can affect fit & durability.

I'd recommend swapping for a narrower BB and trying that. If the chainrings are making the chainstay lighter by grinding it away, try a slightly longer one.