SimDream has stolen those 1993 cars from ACFL.

I don't know which cars he used as a base. But there are still ACFL notes in the data folder.
Well at least he's not selling them anymore.
I have very limited modding skill and I've had a lot of grey hairs when trying to fix them. The 1993 cars were a complete train wreck in their base form. They flip over and crash all over the place. I changed a lot and now they're "ok".
I DID fix most crashing issues with the 82, 83, 84 and 93 cars. Well sort of.
I mean the SD 82, 83, 84 cars still have this issue when they hit the barrier they start "crawling" on the track sometimes.
No one knows what causes this issue, it's amazing. You know when the cars start driving 20 km/h on the track endlessly after a crash. I've tried to change the transmission settings and everything. But they still do this (occasionally) on Monaco and Oesterreichring. Actually original Kunos98T do that too. You never have those issues with VRC, ASR, RSS. But after 10 years nobody has a clue what makes the difference. That is really annoying and it ruins the races. But it only happens on Monaco 1988 and 1979 Oesterreichring. And very occasionally in Detroit 1988.