Specifically, all 70's, 85's, and 90's came/come with Supercharging enabled. All new cars now have Supercharging included (since they are 70's or better). All used 70's or 85's will have Supercharging.
Supercharging was not included by default on 60's. It was $2000 at time of purchase, or $2500 if added later. Most (all?) of the CPO 60's seem to have Supercharging enabled.
40's are not able to Supercharge. 40's are software-limited 60's. You have to upgrade a 40 to a 60 ($10k/$11k, not sure which), then pay the $2500 on top of that.