I know this sounds like a crazy idea. Just wondering if a 12v fan was placed near the right rear manifold that might cool the exhaust manifold enough to keep the expansion to a degree whereby the bolts stop braking. I did something like this to a much lesser degree on a commercial fishing boat to rid the engine room of hot air. I understand the exhaust manifold gets a lot hotter and might be too hot to cool enough to keep the bolts from breaking but I just thought it might be something to discuss.

 

Dumping the stock manifolds for some shorty headers works better. Its the way the exhaust flows thru the stock manifold that causes the problems. Concentrates a LOT of heat in the back quarter. Some good headers/gaskets/bolts, and you solve the problem permanently.