300SEL 6.3 or 450SEL 6.9.

$10k isn't enough to get a really nice one of those though.

AMG C126's are pretty cheap now, I don't think they will be this cheap again. You can probably find with some hunting a super mint 560SEC 6.0 32 valve wide body AMG Hammer...but they go for $20k-$40k or more.

Rare yes, $100k car in 20 years, probably.

600's are also poised to really shoot up in value. More so if they had famous past owners.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200