I tried your link, without success, so perhaps you could have another look at that.

Place an oval port gasket against the manifold to confirm that it does not leave any gaps in the wrong places & if it's all good, then you should be right to go.

On the upside, you have the better head, so the minor inconvenience of sourcing another manifold should eventually yield a better performing engine.
Good one, it looks like you landed on your feet this time.