[SpeedracerIndy]

911st pretty much covered it as far as what I know.

Higher compression (9.8:1), larger intake ports (I think), larger fuel distributor, larger fuel lines, premuffler instead of a cat, more advanced cam timing. Also, the CIS system is very similar to the 78/79 us CIS. There is no O2 sensor.

I would think there are many things you could do to a US spec 81 that could get it to the euro HP levels that are much cheaper than trying to adopt all of the euro bits. SSIs for example would get you most of the way there.

Also 930/10 euro motors require 93 octane fuel, whereas the US spec don't. That means if you are in an area where you cannot find 93, you are still safe to run 87 and don't have to worry about your engine grenading, whereas I'd be screwed!