In 1957 Benbros added a third American car to the Mighty Midget range by creating No.40 Ford Convertible, the other two being No.16b Chervrolet Nomad Station Wagon and No.18 Hudson Hornet 'Hollywood' Tourer. The Ford model was based on the 1956 Ford Fairlane Sunliner Convertible with the soft-top down. 

Like the others, No.40 was a one piece casting with a separate base either clipped or rivetted together. The body included the windscreen and had detailed moulding for the seats and the distinctive side stripe among other features. It was painted in a variety of colours with silver trim added to the large front grille, headlights, rear tail-lights and usually to the windsceen frame.

The base of No.40 Ford Convertible was the same as the earlier No.18 Hudson Tourer and like it had two types, both including front and rear bumpers with overriders and both holding the axles. The first type was a clip-fit base with open-ended bumpers but these were easily breakable so when the rivetted type 2 base was introduced Benbros added strengtheners. There were two rivets, one behind each axle. 'Benbros Qualitoy Made in England' was cast on both type bases and overall they measured 61mm in length.

The first issue of No.40 Ford Convertible was a mid-blue colour and was fitted with type 1 base and large metal wheels on nail-head & crimped axles. This was joined by a yellow variation and then a red one, both with similar bases and wheels. 

The change to the type 2 base happened early on because blue, yellow, and red models appeared with the new base and were then joined by a mid-green variation and a rare white model. All these had large unpainted metal wheels on nail-head or round-head & crimped axles.

At about this time, Benbros became keen on producing models with chrome-plated finish and No.40 Ford Convertible had three variations, two with red seats and trim and one with blue. To complete the 'jazz' effect, the red trimmed models had a blue or red base and painted metal wheels whilst the blue trimmed version had a red base and wheels.

The final group of Ford Convertibles was fitted with black plastic wheels on round-head axles. Colours included blue and red models, both slightly darker than earlier ones, and a new colour of beige, all with silver trim and unpainted type 2 bases.

No.40 Ford Convertible is a scarce model. The blue version with black plastic wheels is the most frequently found, but all others, especially the white variation and the chrome-plated models, are hard to find.