Radiator/Engine temp questions

On my 340, draining the radiator allows access to the manifold fittings w/o leaking, but draining the block is required to access the timing chain cover if that needs replacing. The block drain plugs are most likely frozen in place so take the lower bolts off the TC cover and water will drain from the block. These bolts go through to the water jacket, so they need thread sealant when re-assembling the system.
As said earlier, so much easier without the radiator in place.