Interesting point was that just about the only US V-8 that ended up being
made in the UK was the Buick unit which became the Rover one - and gained
some 20 bhp when being fitted with SUs. Of course that wasn't the only
mod. But I'm not sure what the original carbs were.

The RR V-8 is not an exact copy of any US engine but is very close
to the Olds in some ways and IIRC Chryslers in others. Bristol of
course simply used a blueprinted Chrysler: Jensen used them out of the
box.