The envoy/trailblazers use a 4l65e trans . About the same as a 4l60e only the internals are diffrent. Also the 97 blazer trans will have a bellhousing and torque converter for a 4.3 vortec v6 and will not work with a 4.2 vortec L6. Think the 2005 trans also has a diffrent input shaft compared to the 97 trans.