waited a long time

[haveTBIwantLS2]

All you gotta do is feed the 05's speedo output into your truck harness speedo input...the GM (I should say our trucks) speedos for the most part use the standard 4k feed, even back into my year range (91) and probably a little earlier.
I swapped an 0411 into my 98 tahoe using Lextech's spreadsheet and my speedo works fine, which tells me that it is plug and play. Should be the same for you, also. My 0411 directly feeds my 91's cluster, no issues.
the pinout for your 96 is here
http://www.lt1swap.com/1996_vortec_5.7/index.htm

the pinout for your 2005 is here
http://www.lt1swap.com/2004vortec_pcm.htm

that lt1swap site is awesome, btw.