is there anything different about these motors over an older model one, the one i got was factory rated at 315hp, does it have higher compression different heads, where do they get the extra 20hp from, i am curious?

 

Is it the aluminum blcok model 5.3? They make higher HP numbers than the iron blocks altho i do not know what all if different about them.

 

heads and cam i think.

 

There have been several upgrades over the years in models. Cam on 99-00's are different, there's two different sets of heads but I don't think that made a difference. 99-00's trucks have different pcms which make some difference. 05's and up trucks come with E-Fans which also free up a few ponies.
The new 07 5.3's motors have different heads and I think bigger throttle body.
There's other stuff I can't think of right now.

 

L33 did not come in a reg cab

 

My brother knows whereof he speaks.

 

I heard over on tech and on gm powertrain site http://media.gm.com/us/powertrain/en...RTEC53LGENIVV8
that the 07 up 4.8/5.3 still use the Gen III based heads and intake not the L92 style yet but have the Gen IV blocks for the AFM.
Because the L92 heads will not fit the smaller bore blocks. I have heard that they are working on L92 small bore based heads, so should make more power there if they go with the l92 style heads on the small bore motors.

 

from gm:

 

but my truck is a regular cab, and i am pretty sure it's an iron block, but we are pulling heads tomorrow to replace the lifters so i will find out for sure

 

Just look at the block! If it's painted black it's iron, if is alumium in color than it's aluminum. Easy enough!