Adding threads to differential covers

[m1ac_drew]

I'm looking to explore the feasibility of adding threaded connections to the front and rear differential covers, specifically for temperature switches, pressure sensors and oil lines. Most if not all of the off-the-shelf cooler kits use the drain and fill holes, but I'd like to retain at least the fill hole for it's original purpose and also to have a temperature switch directly mounted rather than in-line on the exit hose.

For those who have removed their diff covers and seen what they are like inside and out, would this be best achieved by drilling and tapping threads directly into the covers or by welding a bung?

https://rover.ebay.com/rover/0/0/0?m...2F371874669271