* Different input shaft: The TH200-4R input shaft is not compatible with the LS engine's crankshaft. An adapter would need to account for this difference.
* Electrical Differences: The controls for the transmission are entirely different. The TH200-4R is a much older design with a simpler control system (likely cable-shifted). The LS engine's computer manages transmission control (usually with a 4L60E or 4L65E). You would need a complex custom controller, which is very difficult and expensive to do correctly.
* Torque Converter: You'd need a custom torque converter designed for the specific application, as the existing converters for either transmission would not work.
In short, while technically *possible* with significant custom fabrication and specialized expertise, it's not practical to pair a 2000 LS 5.3 with a TH200-4R. The cost and complexity far outweigh any benefits. It's far easier and cheaper to use a transmission that's designed to work with the LS engine, such as the 4L60E, 4L65E, or a T56 manual.
