rar files(even old ones) have very good encryption so it's not really a viable option to crack one, unless it's very short, you have a good idea of what it contains and its length so you can narrow things down or you get lucky with a dictionary attack.
Basically, you extract a thing from the rar with JohnTheRipper and use hashcat with a good gpu to figure it out. Some websites do it for money but from the one I've seen, the rar option are disabled, likely because they demand too much power.
And even if you crack it or pay for it, you still don't know the content is real.