Head Gasket Blown?

I have a 95 Olds Cut Sup. the engine has 58,000 Miles on a jasper engine. The heads and plenum were all transfered from my old engine. As far as I know the heads were milled and rebuilt. Four years later I believe I have a blown head gasket.
I was driveing home from work and the temp gauge skyrocketed. When I got home the overflow tank was bubbling. I took out the thermostat and stuck it in boiling water and it did not open. I believe it is a 190 Deg thermostat. I put in a new thermostat and it appeared to work, but a few days later my temp climbed again. I had a local shop flush my coolant. A few days later it jumper again. Finally one day it just would go way up I would let the car cool down and started it again, up went the gage. I let the car set for several weeks and finally decided to do something with it. Now when I start the car alot of white smoke comes out the exhaust. Is it likely I have a blown head gasket or intake gasket, or something else?

There is a checking kit to verify exhaust gasses in the coolant that would verify if it is a head gasket, Carquest and Napa have them. If the upper hose pressurizes right after a cold start, it is usually a head gasket type problem.

I agree with Max, and would add a compression test would rule out a head gasket issue. You're obviously pumping coolant into the engine, either through an intake leak or head gasket.

Yep. The classic symptom of exhaust gas in the coolant is that the car will overheat when idling, but will cool down when driving. Sounds like that to me. Most radiator places will test your coolant for exhaust gases for free.
Thomas