getting ready to drop my new engine with sdpc vortec heads. installing the passenger side exhaust manifold and the very back bolt hole does not line up. does this mean i need to buy headers for these heads? do i look at headers for 98 tahoe or i heard they were based on the impala ss lt1 iron heads. thanks for any help. the exhaust manifolds were off of a l98 iroc.

 

The exhaust manifold mounting bolt holes on vortec heads are the same as any other stock SBC head. But stock cast iron exhaust manifolds are natorious for warping. There is a exhaust manifold spreading tool made by Lisle that helps align the manifold bolt holes with the holes in the head.
makes it a snap to reinstall exhaust manifolds that have warped a bit. Very common problem.