I don't imagine there'd be much point to doing the old Datto A Series head nowadays. They're not as cheap as they used to be, and I'd be surprised if they gave enough extra power to justify the extra work getting the exhaust/engine steadies/water jackets/oilways to work. The Datto A Series was supposedly a copy of the Austin A Series, but saying it's a copy doesn't mean it's identical.
In terms of using a V8 head, you'd have difficulties with waterways and oilways. The most obvious of which, to my mind, would be getting water out of the cylinder head and into the radiator - don't V8's (memory's foggy) usually take the water out the front of the engine, in the valley..?
I vaguely remember reading about the Micra heads..? Both the 1275 and 998? The 998 was never sold out here, and they had very mild cams in them. What I read also implied the bore spacing almost perfectly works, but not head studs. 16v, DOHC.
But they obviously weren't the easiest thing to do, because otherwise they'd all be doing them in the UK, not going further with the BMW head.
The toughest thing with finding a head to suit an A Series is figuring out what's similar. You wouldn't want too big an engine as a donor, you just lose compression. And there aren't that many sub 1.4L 4 cylinder engines in Australia. You also need an engine with a very narrow bore, to fit the valves. Compound that with the unequal bore spacing... Makes it quite a task! Although it would be fun to go through a wrecking yard and try...
Or, if we could get dimensions for everything, which, unfortunately, is something that manufacturers don't tend to provide.
Talking old British motors turned sideways onto Mini gearboxes, weren't there a few Ford Kent/BDA/Cosworth engine conversions done in the '60's? That would've been some work...
