When rebuilding an engine, always use new freeze plugs. We opted for brass freeze plugs, which are a few dollars more than steel plugs, but the brass won't rust out through the years. Our plugs, from Pioneer (available through PAW), were easy to install. You can install them dry, but you should use a sealant to ensure a leak-free fit. Some guys even use Loctite Red to seal the plugs, claiming they'll never leak.