@nprofile1q... No slime blocks, added in 1.8 (which I don't really want to use).
And I doubt it since they depend on observers and some other zero-tick redstone stuff which also don't exist. Like, it'd probably be possible to adapt it, but I know nothing about that kind of brilliantly technical redstone stuff. Plus just making minecarts even more massively resource intensive than they already are lol