This is a 911 based on a 1977 911 SC 3.0.

For historic rallying, the cars need to comply with both safety regulations and technical regulations. 

Safety regulations change as lessons get learnt and equipment improves, items include the strength of the seat mounts, the spec of the seats, harnesses and roll cage. The fire systems are plumbed in and able to be operated remotely. Electrics must have an accessible master cut off for the exterior and the interior. All of which makes perfect sense, after all, these cars may be doing 100+ mph down a mountain in the Alps.

The technical spec refers to the specification and grouping that existed when the cars competed in period. In this case Richard chose the higher performance Group 4 spec in contrast to the similar 911 SC that Adrian runs, which is a very standard Group 3.

The advantage of the Group 4 specification is that there is more technical freedom, one can save weight and add performance. Most obvious is wider wheels and tyres (hence the arch extensions), bigger brakes, coil over suspension replacing torsion bars, adjustable anti roll bars, composite body panels and glazing, whilst additional strengthening can be applied to the body,

The engine of a Group 4 911 can be extensively modified and would typically produce between 270 and 330 hp, whilst you have a wide selection of gear ratio sets available to choose from to optimise performance for particular purposes.