Although the factory EFI manifold affords an easy shortcut to blowthrough forced induction, they are and always will be a low performance antique. (I don't think anyone disputes that) If they were cheap and plentiful, (don't we all wish) I'm sure that there would be countless threads of people whining about their limitations. I will conceed they can be a nice touch on the right car, but to what end, if the car would run harder with a carburator(s)?
You also have to think about the application here. Our friend has a very tidy moggy minor. I doubt whether an unsightly factory injection manifold is going to enhance the appearance of his pristine engine bay.
IMO he'd be considerably better off to have a scratch built manifold made, and use that. He's after more go, without a backward step in reliability. I don't know about there in Aussie, but you could easily make a manifold cheaper than what you'd pay for a factory one here. Plus with a bit of a buff up, it wouldn't look out of place.