After reading it over Mark, I say its up to you. 89S got lucky with the bottle stuff, but if yours is not running white smoke at start up, but after it warms up then it starts to run whitle smoke then overheats... I hate to suggest it, but that sounds like a cracked head to me. If it were a head gasket, it would do the white smoke at start up too. But, since its not doing it at start up, then as the motor warms up, the crack in the head expands, and now you have white smoke, then as it expands further, you are probably getting exhaust in yoru coolant and coolant in your exhaust. That all just seems to be a cracked head IMO, and that's a guess. If the crack is that bad, I'd say the chance of the bottle stuff working, is going to be slim in your case. If you want to keep it, my suggestion would be a patch job, either by a set of used heads and head gaskets, or a used motor. I've been wrong before, but by your description, I just thinking more than blown head gaskets.