Taking a gander at the prototype and comparing it to the current model seems to reveals a set of leaf springs ... Next-gen 2027 GMC Sierra 1500 / Chevy Silverado 1500 Prototype.

Installing a Parallel Leaf Spring Kit in a 1947-1953 Chevy Truck. Rob Fortier Writer Jun 12, 2016. ... The drawback is potentially having to use the stock leaf springs and shackles/hangers.