^^^Indeed, I only recently found this out as I was looking under the hood of a 2000 or so Express. I asked the guy if it had the 6.0 or 5.3 and we looked and it had the 5.7. I figured then that they were the late bloomers obviously....probably lower on the pecking chain.

 

If you are not sure on any transmision exchange. Make sure that the bellhousing is the same on each. In otherwords, all "LS" series transmissions have a bolt hole at the top of the bell housing. The "LT" series do not have the bolt at the top of the bell housing. The top of the bellhousing just comes to a pyramid point. They are not interchangable without the right adaptive flex plate and torque converter. I hope this helps here.