None which come to mind really, all of the mods that had a big impact in AC1 over the years were all scratch made which are from RaceDepartment or paid ones from VRC, RSS, URD, etc...
Except for the RSS, VRC, URD, ASR and a few other mods (very few) all models are stolen/ported from ACC, LMU, Forza, GT and others, with the GT models being the most sought after for their high modeling detail. In fact, many of these models are sold as their own mods using the stolen model, with data modified from the original Kunos cars and then encrypted. Many others use parts from various models to make a single mod and then sell it. To put it in an easy and simple way, in AC1 many have made money by stealing and reselling what never belonged to them.
I think the realistic use of "race modifications" to a car starting off as a stock street car would be more up to a possible car club racing level for amateur types of events in real life used more at a local road race course and not a pro level pure race car which only looks like the original due to the sheet metal hung on the dedicated race car chassis, suspension and drive train set up.
Generally the console version is released some time later than the PC version release.
