[68c10airstream]

You will obviously be using the 2003 complete intake assy on the 2000 motor. The 2000 motor i believe has an egr pipe coming off of the passenger exhaust manifold. Does the 2003 have it also???

When i replaced my 2001 5.3 block the new gm bare block 5.3 fit 99-2006 if i remember correctly.

Do you have a plug in at the front timing cover area on the 2003?? This would be for variable valve timing at the nose of the camshaft area and when gm went to this system they no longer needed egr. (the pipe on the rh manifold)

With the intake manifold removed from both engines it will be obvious what systems are present.