NW141 1/144 Saturn IB Apollo 1
Detail set for ANY Airfix 1/144 Saturn IB kit

Comparison of Saturn IB with Apollo Block II and Saturn IB Apollo Block I (right side). The NW141 conversion and detail set contains whole upper portion of the rocket (grey color), so you can use ANY Airfix Saturn IB kit including the older one with completely incorrect Apollo spacecraft (imcorrect Service Module surface, diameter of the spacecraft is about 3 mm smaller).

The main difference between Apollo Block I and Block II is completely different surface of Service module and different Apollo Boost Protective Cover (a cap over the Command Module).