If you're just looking for the drag coefficient, google does great. Just google for the car name and "coefficient", or maybe "drag coefficient". Someone recently posted a site that had a whole bunch of cars listed with their drag coefficients but it seemed to be mainly 1990-1995 models.
They don't list the drag on pickup trucks. I tried to lookup what the beast was and it wasn't listed. I figured it wasn't much different than a new one, so I searched year 2008, and still the drag was not listed... I don't imagine it was all that great anyway. If they did list it it'd probably be listed as "Cinderblock with rounded corners and covered in lard"
Actually, it maybe even decreased slightly... The 98 Sierra has perfectly flush doorhandles, I do not believe the current models do... I think the biggest improvement they made recently to the trucks is their active fuel management system.