5.3 Aluminum and iron blocks

[XR Man]

Why did GM start making an aluminum block 5.3 and keep the iron block? I know the advantages of aluminum but why not change over the entire line? What trucks come with which blocks? Is the HP more on the aluminum? Any problems specific to the aluminum block?

 

Thanks

Bryce

[Buggle_96]

Im not sure about 06, but in 05 you could only get the H.O. engine in th ext cab half tons, and i believe they had to be 4wd.