I'm pretty sure the 2wd cossie is 14 x 1.5, about 3/4" long.
I just use either loctite 5900 or 5910, or steal my dads hylomar, as it's free!!
I have always used sealant on the threads, started doing this when I needed a new plastic washer on a sump plug, on a renault I think it was about 25 years ago.
I've never seen a single drop leak from any sump plug this way, even those later where I didn't even bother to fit a sealing washer that didn't work in the first place.
The only issue I have found is cars with pressed steel sumps, the sump rots, as it is no longer covered in oil, but this takes years and years, if pressed tin sumps I would put underseal etc on them to stop the rust.
There isn't really any chance of hylomar getting into the engine, as it has to get to the end of the threads to start with, and even if it did get into the pump, it is so soft it would cause no harm, and would soon be mashed down.
I don't use loads of it, I just put a 5mm dab on my finger and spread it around the whole bolt, all the way from top to bottom, firmly so it is just in the threads rather than sitting on them, when the plug is tightened up, it will spread out over the sump plug head just wipe off, this shows it is well sealed.
tabetha