Draining & replacing coolant / engine block drain location?

If your engine is like the 3.4L XK-120 engine, your block drain is on the left hand side near the oil dipstick.

I converted the 120 to Evans last winter. You definitely want to use the prep to absorb any residual water before putting the coolant in. The nice thing is that the prep fluid can be re-used (but you have to boil out any water that it's absorbed). Also, getting the tool to read the % of water (once you've installed the coolant) is useful. They say that their coolant will tolerate about 5% water - when I got done, I was below 1% (iirc).

Finally, don't forget to do what you can to drain the heater core, too. I disconnected the inlet side and blew air through it, not sure if it will be that easy on your car (very easy on the 120).

Good luck.