Released 40 years ago, the Porsche 911 Turbo has undergone a lot of modifications, some of which include the switch from an air-cooled to a liquid-cooled engine, the adoption of a midship layout, and the upgrade from a five-speed transmission to a seven-speed transmission. To compare and see the progress made, Magnus Walker test drives the original 1975 model alongside its 2015 counterpart for a thorough analysis of the two. Watch the video above for the outcome.