Not entirely. The LF6 was used in 1999, whereas the LU3 was used in 2003. The biggest difference is that the LU3 uses multi-port injection. Compatibility is possible, but I believe you'll need the corresponding ECM with each engine.
No, it isn't. They both displace 4.3 liters, but the 99 has the LF6, whereas the 03 would have the LU3 with multi-point fuel injection.
Chrysler did.
I.C. engine stands for Internal Combustion engine that cars, trucks, and airplanes use.
A combustable engine
In Indonesia some of Jeep CJ7 had this engine.
engine controle unit
Duramax
UPS trucks
Trucks - 1999 Rolling Thunder Part 2 Engine Fitment was released on: USA: April 2010
Thomas the Tank Engine and Friends - 1984 Trucks 4-8 is rated/received certificates of: Australia:G
Trucks - 1999 6 Liter LS Truck Engine Swap was released on: USA: January 2013