If there's a temp sensor just ahead of the thermostat, it might help to remove the temp sensor so you can remove the radiator hose fitting more easily. In some applications there's just enough room to slide the radiator hose fitting forward and out. No room to pull it directly away from the block. Mind you remove only radiator hose fitting bolts, not the thermostat housing bolts. Doing so you might upset the gasket between the thermostat housing and the block.

Sixto
87 300D