What are the weight ratings on rear springs?
Not sure exactly, may need to contact a dealership for this information.
First off we will note that the two most understood spring terms out there are Spring Rate and Load Rate.
Spring Rate
A spring’s Spring Rate is the amount of weight required to deflect a spring one inch. The lower the Spring Rate, the softer the spring. The softer the spring, the smoother the ride.
Load Rate
Load Rate, on the other hand, is completely different. Load Rate is the amount of weight a spring is designed to carry when deflected to a certain height.
Source: https://www.eatondetroitspring.com/spring-rate-vs-load-rate