truck engine master 72 and 73 ?? confussed

[ianrobinson]

I have 2 chevy 350 engines one is out of a 1 ton 73 van and the other is out of a 72 1 ton motorhome both engines are 4 barrel carbs blue intake and valve covers but block is orange the suffix codes on the 73 block is
K12 18 CMJ 74L436231 and the suffix codes on the 72 1 ton is
K02 08 CMJ 75L312202 everyone keeps telling me its a 74 police engine turbo 400 or a 74 chevelle 145 hp why would both trucks have car engines 2 years newer then what truck they are in or is it no one has the truck suffix codes only the car suffix codes ? i am also from ontario canada mabey we have different stampings in canada any help i would really appreciate ... thank you in advance i am hopping someone has the same engine or gm just put these engine in the 1 ton trucks