RE: over heating & heat transfer

> Prior to refilling with the proper coolant should I flush the system
> with something; if so, with what?

IMO tap water is fine, unless your water is super-hard.  In that case, I
might consider a flush with distilled water.

And of course use distilled water to mix your coolant.  Only takes a gallon
for a TR3, should be less than $1 at your local grocery store.

Did you have the radiator shop test the radiator for efficiency ?  That
turned out to be my overheating problem last time.

Randall