What trucks got heat stoves in 1969?

[IronCanine]

At what point in 1969, did heat stoves appear on our trucks? Below is a 69 Blazer that is purported to be low miles and looks relatively honest.

1) The paint color gives away it's 1969 status
2) The air cleaner assembly is the earlier version without a provision for the heat stove.
3) Blazer production began later in the 1969 MY
4) This truck has A.I.R. manifolds and no pump. Not surprising, but just to point out that it's not untouched.