flushing the cooling system?

I'm putting my '97 Passat back together after a prolonged head replacement.

It included a timing set/water pump, and I'm adding a frostheater.

Have ZERO idea how old the antifreeze is (was) and I'm considering flushing the system, while I wait for the last of the parts to come from frostheater.

...does anyone do this??

I know citric acid is really common, in the "MB diesel" community..

I'm primarily looking to get something in the head, so I can start running the engine, to make sure there aren't other problems.

I don't think putting plain water in there is in my best interests..

The weather should be above freezing this week, btw.. If it's running, it's also not a problem if it does, for that mater.. I'll just go for a drive!

I did all the same repairs/updates 1.5 years ago. I initially flushed the system out with water and ran it in the garage with water only to test for leaks. Once no leaks, I drained it completely and added G12 at proper dilution.