Those are indeed new kits, and they have new molding technology. The detail on the parts is astounding! These two kits (one Ford V8-60, the other the 110 Offy) are among the the best kits I have ever built. However, along with the above good news, there is bad news. Sales of the kits were disappointing to Revell, and there will be no more production. They are disappearing off shelves, never to be found again. So if you want one, you need to get them while you can, or be willing to pay eBay prices!
They are just a bit fragile, which is inevitable given that the frame and suspension parts are scale diameter/thickness, not like old monogram kits with heavy suspension. As you can see from James' photos, the engines in particular are little jewels, almost worth buying a kit just to build and display the engines.