Need some help on some numbers.

[ArkGL01]

I have found a Cheyenne SWB 402 truck. Nice truck original interior but they added buckets and has original AM radio. No glove box data sheet because they did paint it before he got it. The 402 has original linkage and carb. Guy has owned the truck for 20 years and knew who had it before that for 5 years. The only problem is the number on the motor is TO327TKX.. TKX runs to a C20 truck. I know they put c10 motors in some of the c20s but did they put C20 402s in the c10s. The truck was built in st Louis. I don't want to buy a non matching numbers truck. Any information would be appreciated.