You should be able, once you have the manifold off Tim, to be able
to have it welded at a machine shop or engine crank regrinding facility,
we used to have exactly the same problems when I worked on SAAB,s
in the late 80.s on the classic 900 turbo,s, they used to be famous for
cracking exhaust manfolds Tim. not very costly either
manifold was though
fitting was a right pig too.
I hope this helps Tim
Vince.