The web site was recently opened for 73-87 GM pickups AND the 88-91 K5 Blazers and Suburbans.. The rounded line or the mislabeled "squarebody". These trucks are a bit more plentiful and less expensive than getting into a 72 and older truck (for now).
In my area, the market for the 73-87 GM trucks seems to be pretty inflated compared to just a couple years ago. They are getting very popular. Occasionally I see one listed for what seems like a sensible price but that is the exception rather than the norm.
Neighbor has a very original patina’d 73-ish truck that I’d like to have. They are a transmission shop and this is one with signage on the door that I’d assume had some sentimental value. They lowered it recently. Not my thing, but it still looks pretty good.