350 Exhaust Manifold Nuts

I'm going to install a dual exhaust system on my wagon.What is the easiest way to remove the nuts from the exhaust manifold flanges to remove the crossover pipe? Looks like they haven't been turned in years,but not too much rust.I just don't want to snap them off.Any ideas? ......John

 

soak them with PB Blaster 3 or 4 times over a 24 hour period and you shouldn't have any problems.