What size motor is the correct fit for a 1993 Ford Festiva with an automatic transmission?

The 1993 Ford Festiva with an automatic transmission came with only one engine option: a 1.3L inline-four engine. There isn't a choice of motor sizes; it's a single, specific engine. You won't find a different size motor that's a direct "fit" without significant modifications (and likely making it unsuitable for reliable operation).