The transmission bolt pattern statement was 100% accurate at the time it was written about 15 years ago. If Chevy/GMC changed its bolt pattern for some newer engines, that would be good to know, and I appreciate your input.

For a little historical perspective: GM established the Chevy transmission bolt pattern we're talking about here with the introduction of the 1955 model year 265 C.I. smallblock gas V-8 used in its cars and light trucks. That bolt pattern was carried forward into GM's 1960-90s era 396/427/454 C.I. and 8.1L bigblock gas engines. That bolt pattern was carried forward into (as Greg mentioned) into all Chevy/GMC full size gas and diesel powered light trucks through the entirety of the 6.2L/6.5L production. And finally, that is the same bolt pattern currently in use by the Duramax 6600.

Jim