Frame Design Changes Exposed

I was out of town recently and found a new 2001 Ext 1500 at a Chevy dealer. I checked out the frame and there were enough other trucks (100+) to compare with that I was able to chronicle the visible changes across 99, 00 and 01. The  99 and 00 both had a wimpy bolt-on transmission crossmember that was not braced to the frame. The 01 and the later (appeared to be after 3/00 builds) 00's , had  welded mounts on the frame for the transmission crossmember. These mounts had 90 degree bracing to the frame. They also dropped down below the rails to accommodate a larger crossmember. The 01s add two braces that run from a foot behind the front wheel on each frame rail to a central point on the crossmember where the front bushing of the lower control arm attaches to. This effectively provides another 90 degree brace to the frame. The 01 also has a brace that runs perpendicular from the left to the right frame rails about 8-10 inches in front of the driveshaft carrier bearing mount.
Below you will find digital pictures of these trucks, including the frame stickers that show the build dates. The 2001 showed a 6/21 date. I saw many 2000s in the 6/8..6/9 range but no new braces. I even have several pictures of a brand new complete 4wd frame leaning against the body shop wall it had no braces and was built in Canada on 6/6. It did have the complete transmission crossmember attached. I would like to see that shop ticket. Could it be vibration related????  I have many more pictures I will post later. Some are suspension others frame, etc.

Click on Thumbnails for a Larger View
2001 Silverado 2wd Ext Cab 2000 Silverado 2wd Ext Cab
2001 Trans Crossmember 2000 Trans Crossmember
2001 Front Brace 2001 Rear Brace
2001 All Braces Complete 2000 K1500 Frame
The 2001 I saw

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