need help! what motor is this?

[migtek02]

Thanks,
the head cast number is 706.

[SLO TRUCK]

706's it should be a 5.3 or 4.8. The block should marked like Nate said.

[migtek02]

i belive its a 2003 + 5.3 due to it being a flex fuel setup since the flex fuel started in 2003 and Gm did not offer a 4.8 FF option. Rigth? what years used the 706 heads?

[GasGuzzler]

FF started in 2002 as stated above.

[migtek02]

Thanks guys for your help.