My 1996 5.8L didn't come from the factory with exhaust manifold gaskets. I'm putting it back together and was wondering If I should put some on it, or just put it back like the factory did?

 

The factory didn't use them because when the engine was built/installed both the cylinder head and exhaust manifolds were new and the mounting flanges were smooth, straight, and rust free. Unless you plan on having these mating surfaces machined smooth and flat use some kind of gasket or some hi temp silicone sealer depending on the application.

 

Definitely want to use gaskets if you live where snow and ice can get up into the manifold/head juncture. My 96 E150 came from Iowa and had exhaust leaks due to road salt from snow//ice melting on the road getting between the manifold and head.