It seems the problem is with the top tank being thin, so each heat cycle it went threw it would flex, and over time crack the solder joint. I can't blame it all on the radiator, the guys that recored it had to do the top tank twice because of leaks, but the front side of the top is really thin. It could be just a poor repair, but I have been sealing leaks for 5 or six years now. They are all ways at the top front seam, and leak just enough to get the firewall spotted and slick.
I would think with A/C and a no pressure system you might have cooling issues. You should consider a overflow tank so at least your coolant won't hit the pavement. It should return to the core once it cools down and the extra tank could be open to the atmosphere so you still have a zero pressure system.
Building a new top tank out of heavy brass would probably cure the problem of the flexing and pressure and wouldn't be to hard to make and get soldered on.
Joe
