When Ertl developed these kits they modified the AMT Kenworth W925 kit rendering it no longer viable. Round2 repaired the altered parts and brought the W925 kit back. In order to bring the T600 kit back they would need to a) Undo their repairs to the W925 making the W925 and Alaskan Hauler not viable, or b) create new tooling for the parts. Either way they would have a kit that was not well received due to it being a not-quite-right 1990-ish T600 with the engine, chassis and running gear of a 1969 Kenworth W925. Everything was a generation of design out of whack.