Brendan, as far as the Bars Leak Stop stuff, I have used it and it works
great, but I wouldn't use it on my 'baby' if you know what I mean. This
stuff is distributed throughout your cooling system, compromising your
radiator efficiency. I have not heard of anyone running tests or cutting
into a radiator to see the effects of Bars, though. As for me, I will use
it on my daily driver junker, no questions asked. I have spare radiators
if they fail. I have encountered the leaking head (just a drip, not
pouring out)added Bars and not encountered another drip for an other 150K,
at which time I added some again........and so on. So, if it's your baby,
I wouldn't do it.
Check out Benny Boy's site. It has great instructions, complete with
video, on how to do the heads. Once you see how he does it, you will be
chomping at the bit. Good luck. Miguel