Can a 1989 Festiva cylinder head with carburetor intake be replaced off 1992 fuel injected intake?
No, a 1989 Ford Festiva carburetor intake cylinder head is not directly interchangeable with a 1992 fuel-injected intake cylinder head. They are fundamentally different designs. The porting, bolt patterns, and even the head gasket surfaces are likely incompatible. You'd need a significant amount of modification (likely impossible in a practical sense) to make them work together. Attempting this would require major custom fabrication and likely wouldn't be worthwhile.