Here is a Powertrack regular, the Renault Alpine. It is quite a curious entry as it is available in so many variations. The differences are subtle, enough to make you wonder why they bothered..
The standard issue car is in the foreground right. This is common to both US and UK markets and is the only car here shown fitted with an Airbox behind the drivers head.
The later car, (back right) has the same livery but is without the airbox. It was also moulded in colour, while the standard car was spray painted. The latter appears waxy by comparison.
The black yellow Renault is much more faithful to the real racing cars of the seventies but quite scarce in Matchbox circles. There is no reference to this model at all in any period literature. Note the drivers helmet is red for these versions.
The other car is the Powertrack Plus version, more of which later. The last three cars mentioned are all without airboxes. The mouldings clearly have no fill in panel, so when Matchbox decided to mould in colour they also deleted the airbox.
Apart from the production models, check out this prototype from the UK Powertrack instruction manuals of 78/79. This car is significantly different, there is an airbox, but the rear wing is alot smaller. The front headlights are round and there are 4 slots in the front splitter. The grilles over the front wing are smaller and the driver is seated to the left of centre. The cockpit is a squarer profile and there are no cooling slats over the rear bodywork at all. The stripes run white and the drivers helmet is red.
Obviously, this is a pre-production example and could be made out of wood for all I know. If a working sample of this turned up its value would be significant.