PROCAR BMW SERIES ALLOWS TRUE MODEL CAR RACING
True model car racing is the reproduction at scale of races having been contested, or in the immediate past (e.g. the 2008 Petit Le Mans ALMS as contested in 2009 at the Toronto Endurance Worlds, or the Ferrari F430 Challenge Final of 2007 as contested at the Toronto 124 Sprint World Championship) or in the further past (e.g. The 1970 Le Mans 24 hours as contested at the 2005 Franco Gianotti Trophy at Aalst). In most cases the reproduction is only partly perfect as not all cars in the original 1/1 race are present at the 1/24th reproduction (at the Petit Le Mans of Toronto not all GT1 and GT2 cars will be present; at the Le Mans race in Aalst only 32 of the 55 cars were present at the model car version).
If we consider all 1/24th models actually available, I see only two possibilities to organise the perfect model car race, nl. as a copy of the 1979-1980 PROCAR BMW series or as a copy of the IROC races of 1974-2006 in the States. Number of cars having been involved in those series was restricted and complete model car versions are easily available. Of the two the PROCAR series shows certainly a higher attraction than the IROC as famous F1 racers entered in 1979 and 1978 that PROCAR competition.  
PROCAR was thus - just as IROC - a one make series, pitting professional drivers of the F1 World Championship. Jochen Neerpash, head of the competition division of BMW Motorsport GmbH, was the father of the initiative. For that competition, having started in 1979, the street version of the BMW M1 was tuned to a 3.5-litre Group 4 version with 470bhp instead of the original 277bhp, allowing a top speed of 311 kph and an acceleration from 0-100 kph in 4.2 seconds. BS Fabrications constructed five cars for the BMW Factory team, in the course of the season four more. Cars for other competitors were constructed by the British Project Four team of Ron Dennis (38) and by Squadra Osella Corse (2), using themselves a car in competition, and selling the other cars to such teams as GS Tuning, Schnitzer, Tom Walkinshaw Racing, Max Eggenberger, Max Heidegger, Alimpo Sport, etc. Price of the car was up to $ 60,000. The winner of the series received a new BMW M1 Group 4.
The races - no longer than a half hour - were contested as curtain raiser to the European F1 Grand Prix in the mid-season. The five best qualifiers at the Friday F1 qualification session received a works BMW M1 and could - irrespective of their qualification time with the M1s - always start from the five first places on the grid. As the cars used special Goodyear tyres several Formula One drivers were not allowed to compete due to contractual obligations with competing tyre manufacturer Michelin.  As Scuderia Ferrari and Renault raced on Michelin and were selling road cars themselves, they did not allow their Formula One drivers to participate. The other cars went to famous drivers of road racing (among them several ex-F1 drivers and several later F1 drivers). In 1979 e.g. twelve F1 racers of that year entered the PROCAR Series. For Jody Scheckter and Gilles Villeneuve (Ferrari) and for Jean-Pierre Jabouille and René Arnoux (Renault) such was, however, forbidden by their employer.  
The BMW M1 was intended to be a direct opponent to the Porsche 935 in Group 5 racing. Unfortunately the FIA changed the rules by requiring 400 copies of each car before they could be tuned to Group 5 cars. When BMW eventually had manufactured its 400 cars Group 5 racing was replaced by Group C racing, so that it never came to a direct opposition between the Porsche 935 and the BMW M1 Group 5 (except at the 1981 Nürburgring 1000-kms, where a BMW M1 Group 5 won the race when it was flagged off after 2h16min due to the fatal accident of Switzerland's Herbert Muller.