Want to put a 2008 5.3 in my 2003 5.3 ECSB 4-wheel drive. Mine is an iron block and the 2008 5.3 is an active fuel management engine with aluminum block. Was told the knock sensors are in a different location and I need to change the lifters. Any help in enlightening me would be appreciated. Thinking about putting in a cam and having the 243 heads ported. Thanks, Wayne

 

You should check the color of the crankshaft sensor connector (passenger side block, near starter mount)... If it's light gray, the engine is a Gen IV with the 58x reluctor wheel and timing cover cam sensor. You would need to make a lot of changes for it to work in your '03 truck.

The good news is it has the OE high volume oil pump GM installed in the AFM engines.