Gen 2 US to Gen 2 Euro 560 Swap

You don't need to swap anything. The computer doesn't know what engine it is running - it has no "awareness". If you are satisfied with whatever year and refinements are in the electronics that are in the destination car then leave them. The easiest of the easiest is to use a FD from an early Euro. No computer at all. It will run an engine all by itself on an engine stand with no car in sight. All you need is fuel pressure and spark.

lsfeder said:

I had read somewhere that the harnesses are the same on all Gen 2's, both US and Euro. Is this not correct? Also, I am pretty sure the computers and EZL need to be switched not because of "awareness" but because of the ignition advance and mapping that the Euro electronics have. If I were to use the US spec ECU and EZL I would be loosing out on potential HP no?

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original post - If you are satisfied with whatever year and refinements are in the electronics that are in the destination car then leave them.

Most of the HP comes from engine mechanicals like the exhaust manifolds and cylinder heads.
Personally I would just plug the engine into the US electronics and have it smog tested. THEN I would worry about swapping in the Euro boxes. It would be interesting to see which is cleaner. Then, an obvious option is to swap back to the US units whenever you need a smog test.