Complex sentence: It is designed by Steve Harper to be essentially similar in appearance to the Scorpion III, but with an extra wheel and slightly larger dimensions the Scorpion IV is an open sports car constructed from a fibreglass covered steel space frame chassis.
Split into simpler sentences: It is designed by Steve Harper to be essentially similar in appearance to the Scorpion III, but with an extra wheel and slightly larger dimensions. The Scorpion IV is an open sports car constructed from a fibreglass covered steel space frame chassis.