Here's what I did:
I had a pair of Kappa 62.1i which list as 6-1/2" and found they just did not exactly fit the plastic bracket on the rear doors on my 2001 K2500HD. I thought about bending back the metal rim and drilling new holes, but checked on another website where the rear doors on a 2001 K1500 Suburban took 6-3/4" speakers. I own one of those, and compaired doors with my pickup, and found them to be identical. So that is where the 6-3/4" Kappa 652.5i came in. These are great.
All this after trying the 462.3cfp - which was not all the way to my liking.
Also take note of hoot's advice - when hoot hoots, you gotta listen. I did have to shim the bracket a little to move the speaker closer to the grille, letting the magnet clear the window path. Installing aftermarket things inside doors often takes some trimming somewhere.
2001 2500HD DuraMax/Allison Crew Cab 4x4 SWB - WRECKED!<br />2003 2500HD DuraMax/Allison Crew Cab 4x4 SWB Lt Pewter/ Tan Leather<br />2003 2500HD DuraMax/Allison Crew Cab 4x4 SWB Dk Green/ Tan Cloth