I should check!
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Cant see from here but I recall when I looked at the numbers on the heads my gpa had on a shelf in bags were powerpack ones for a 283 but when I looked at these ones, I recall either a steam port being present(I couldnt tell ya right now based on that pic, its also 10 degrees out rn) or the numbers coming back as a late 70s 400 (Meaning they probably, my assumptions, came from the 78 k10's original 400)
However, it confused me because my trucks original 350 is the one without heads sitting upright in the back of the shed. Unless he got rid of them or i havent found them yet, It mildly confuses lol. But Ill have to check some numbers to be sure. The head on the left, to my best research, either goes to a tractor or a old inline engine that I couldnt figure out yet. But the two covered partially by the wheel are the ones I was referring to.