'89' Lxi battery Size

I've got two Questions concerning batteries;

My owners manual states that the battery should be 12v-50Ah

But car batteries seem to be rated in cranking power like 550AMPS, for example.
How do I convert that 50AH to cranking Power AMPS?

Also, can you harm the electrical system by useing a too high rating?

Thanks, Jim

Batteries go by group number which sets CCA and terminal configuration. Look at the old battery. It is probably a GRP24.