Yeah! Exhaust Mainifold bolts!
Bit of a bugger! Removing the heads 'in situ' awkward to get all the manifold bolts out of the head, while the down-pipe flange studs are a real pita.
Probably least hassle, if you can, to split the pipes at the flange, but as said, the studs are notoriouse for stripping, shearing or bending, and you have to 'wiggle' the heads out of the hole with the manifolds on.
But I think I'd rather risk that than the skinned knuckes trying to get the rearmost manifld bolts out of the head in the restricted access under the bulkhead.
Once off, manifolds come off the head easily enough, and you can drill out the old flange studs and replace if they are in bad shape.