Temperature gauge installation?

I want to install a mechanical trans and oil temperature gauge in the the trans pan and oil pan. Are there adapters available so I can use the drain holes or do I need to weld a bung in each
pan? There are 2 kinds of bungs I see (aluminum and steel) so which one? The fittings that came with the gauges (Autometer) won't fit into the drain holes so I thought the simplest way
was a drain hole adapter. Don't claim to be a welder either. Any suggestions?