40mm DCOE side draft Weber. Also 40mm DHLA Dellorto. Same thing, vaguely. They bolt to the same manifold.
Yes, those manifolds are easier to come by. Hell, I think you can even pick them up new. But unless you've done head/ Cam etc, and (I have three sets of them, so this is an honest figure) feel like spending $1000 to set them up properly, I wouldn't be looking at them.
SU's are a nice compromise, but you wont necessarily find a manifold in a day.