Manifold bolts should not be over- or under-tightened, so use this type of wrench with a foot/pound scale
Unfortunately, if the bolts were tightened so tight that they stripped, I doubt ... 
inaccessible nuts and bolts, like the nut holding the exhaust manifold bracket to... [DOC] [TLE] chapter 4 - Jones & Bartlett Learning [PAR] Identify types of threads, nuts and bolts.