Hi Roy,
The whole "Model 1941", "Model 1942" designation system is something made up by historians and modelers to inject a little structure into the discussion. At the time, the Soviets did not distinguish between the KV-1 variants, except by armament, unitl the KV-1S appeared.
The generally accepted, albeit arbitary, nomenclature is that the up-armored hulls with the squared-off rear hull overhang are Model 1942s, regardless of the type of turret. Earlier hulls with the rounded rear overhang and ZIS-5 guns are Model 1941s, and those with F-32 guns are Model 1940s.
All the Model 1942s were completed by ChKZ (ChTZ was renamed on 15 October 1941 after the LKZ factory and portions of KhPZ were relocated to Chelyabinsk). The hulls were actually manufactured under subcontract by UZTM in Sverdlovsk (short applique armor on the driver's front plate) and Factory No.200 in Chelyabinsk (tall applique armor). UZTM switched to T-34 production in July 1942, and the final Model 1942 and the KV-1S hulls were all built by Factory No.200.
Model 1942 hulls were fitted with three different types of turret by the factory; simplified welded turret (as depicted in the Trumpeter/Hobbyboss kits) introduced in September 1941, the original cast turret introduced in early January 1942 and the reinforced or "lightweight" cast turret introduced in late January/early February 1942. With a little cross-kitting of the Trumpeter and Hobbyboss kits, you can make any of these variants.
Cheers,
Neil