In your case, for a direct swap, you will need a 4L60E used in Silverado's with a 4.3-V6 / 4.8-V8 / 5.3-V8 from 1999-2004. 2005-Newer 4L60E's had different wiring and main harness plug. 2002-Newer 6.0L 1500 Vehicles used the 4L65E and 1999-Newer 6.0L 2500 Vehicles used the 4L80E, which in either situation, will not work for you.
Originally Posted by 76larkman
my tranny guy claims 04 on trucks was first year on the 4L65E internals. Far as I know early 07 trucks were same as older
The 4L65E was introduced in 2001. The 4L65E was only behind the 6.0 (At least in trucks and SUV's, and was used in the Silverado SS, Sierra Denali and NBS Vortec Max Trucks. NNBS Vortec Max trucks received the 4L70E until early 2009.
The 4L60E was used in Silverado's up until 2013.
2005 (Some 2005's) and newer added a Speed sensor inside the pump housing like the 4L70E.