Use the original flange pattern (obviously) and then either fab or have fabbed a 4->1 setup. You could also use a silvertop manifold and cut and reposition the pipes and that would save some work. This is where you put some though in, you can go 4->1 into the pattern for the turbo you intend to use or 4-1 into a large more universal pattern then make an adapter for the turbo you land up using. Either is going to work but if you fab the original manifold for a small turbo inlet and change later it is harder to change.
This is a tacked up manifold, it doesn't have to look pretty it just has to work
