my buddy Pontiac Mike found this write up on the early LS GM water pumps and thermostats you mind find helpful / useful
GM Gen III & IV V8 Engine Thermostat Identification:
GM has changed water pump and thermostat designs on the Gen III & IV V8 engines (LS engines) several times over the years. Make sure you have the correct thermostat for your vehicle. This is especially important if you have had your water pump replaced because in some applications the service replacement pump and thermostat may be different than the original equipment pump and thermostat:
https://www.lingenfelter.com/PDFdown...ats%20List.pdf