Loc-tite makes a green formula thats called "Sleeve & Bearing Retainer" It's pretty much permanent until you take a torch to the bolt and heat it up.

It's designed to lock steel sleeves into aluminum cylinder blocks. We use it on the main caps and rod cap bolts in drag racing engines. It's high heat and extremely high strength. It doesn't come loose until you use a propane torch and heat up the head of the bolts. Heat it up for a few minutes and let it sit to soak the heat into the bolt. You'll probably have to repeat this procedure at least twice before there is enough heat in the bolt and surrounding metal to soften the loc-tite.

I've used it on several mufflers over the years. Works great. The only thing I would caution against is trying to loosen the bolts without first hitting them with the torch. You'll just snap the head off the bolt and then you're really hosed. It IS permanent and you WILL NOT get the bolts out without a torch to soften the stuff up first.

I don't use it anymore though. I drill the bolts and use safety wire now. It works good and it comes off a lot easier when you're ready to take the bolts out.