Here is an update on this thread.

I did a lot of research on head gasket sealing potions. There seems to be 3 types.

First, there is the Barrs sealer type which has copper flakes in it. The idea is that the copper flakes get lodged into the leaks in the gasket. It gets hot there and they melt and stay put. I have two friends who used this in Subarus with head gasket leaks, and they reported 100% success.

Second, there is the Sodium Silicate (aka waterglass) type (Steel Seal, Bears Leak, others). This stuff apparently cures at a specific temperature.

Third is the type made by Titan Sealers (actually, they claim to be the only maker of this type). It is a polymer that is designed to cure at a temperature that is high enough that it only occurs at the head.

I decided to try the Titan sealer stuff.

I drained the radiator and block, removed the thermostat, and bypassed the heater core with a piece of copper pipe. I put in the titan seal goop and filled with water. I did 3 run cycles of 20 min idle, 20 min rest, then overnight cool. The next day I took it for a drive, and amazingly, no overheating.

I'll continue several test drives like this before putting the stat back in and reconnecting the heater core, then draining and filling with anti-freeze.

So- not totally out of the woods yet, but it is looking good so far. How long will it last? Who knows. But I do know that I do not have the time to do a head gasket on this car.