Exhaust manifold connection to exhaust pipe

I recently installed an exhaust manifold to the engine in my truck. It seems not to line up flush with the three studs on the exhaust flange, there appears to be a slight slant; I am not sure if I have the right exhaust manifold for the truck, is there any difference in exhaust manifolds for this series trucks? 1987 B2000 or B2200? Could it be sagging down? Should I try jacking it up a little underneath the truck?