1966 C10 LB with '69 Small Block?

[Just1randall]

Hello,
Recently acquired a 66 long bed project truck. Seller had told me it had a 283.... I can do an oil change and not much else, so had no clue.
Now doing some research and getting some mixed results.
What might I have here?

ViIN stamp on front passenger side of engine =19Zxxxx (1969?... were 283's still being made?)
Other stamp to right of VIN=T0916HR (HR is for 350?)
Oil tube attached to manifold= not on 350s?
'Camel' humps at front of engine casting=350?
Pic should follow.

Thank you