UK engines had moved on to the 3.2 by then, so our experience might not be directly relevant, but by 02 they had gone to using a fixed idler for the lower right roller.
It doesn't actually matter which one you fit. Adjustable idlers will still work with the later engines. It is important that you replace it, however, as it's the bearings in the idlers that are the main cause of cam belt failures.
As to the castings, I think I'm right in saying that the latest ones, as would be on an 02 engine (here, at least) were marked "01", so it's possible it has been fitted with the incorrect one in the past.
I think I'd be inclined to try the 01 casting first with either lower idler and see if it times up OK, with plenty of travel left in the spring tensioner and plenty of clearance between the idlers and pullies. If that doesn't work you can always swap the two new idlers onto the existing casting and re-use it.