[66 C10 383]

I'm not sure if these parts came from the same truck or not. When I bought the engine and trans I told him I'd rather have a DBW setup so he included all the parts I needed.

Eric, I think you're correct, it does look like a 3 rather than a 5. There's just enough of a scratch in the case to obscure the top portion of the number. Remove the top part of a 3 and it can look like a 5 ...

When I google 12575059 it comes up as a discontinued set of GM heads so that's obviously not correct. When I google 12573059 at least it comes up as a TAC module ... LoL Amazing what one little number can do ...

Thanks for the info on the Flex fuel injectors, too. I may look into seeing how difficult if would be to run this as a flex fuel engine.

I'm sure I'll have lots of other questions ...