Replacement radiator for IS300

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When replacing the a/c condenser recently (and that's a whole separate story....) on my 2002 IS300 Sportcross auto, I noticed what looked like a slight weeping leak from the radiator.  It's not impossible that the tubes/fins might have been damaged in the process of removing the old a/c condenser, as it's a tight squeeze. 

So I have been looking into getting a replacement radiator, and I'm getting a bit confused by the astonishing range of specifications, brands, and prices. 

Leaving aside the custom-welded high performance aftermarket rads (which aren't cheap), it seems there are various differences in what is available.

1) auto v manual.  Radiators for auto transmission vehicles have to have a transmission oil cooler - which means a small separate cooler along the bottom of the rad, with two "extra" hose connections for the oil lines. Rads for manuals don't have this.  But... it seems that manual vehicles can use the rad for auto vehicles, and just leave the  oil cooler unconnected.  Obviously it's not possible to do it the other way round (you can't put a rad for manual-only into an auto vehicle).  Problem is, a lot of aftermarket suppliers don't make clear whether their product has the oil-cooler or not...

2) tube size.  The Lexus OEM radiators apparently have 25 mm diameter cooling tubes, whereas almost all aftermarket ones have only 16 mm.  Some say that in most conditions this doesn't make much difference to cooling-performance.  Anyone care to comment?  The difference is that 25mm rads are only available as Lexus OEM and twice the cost of aftermarket alternatives, which are mostly 16mm or don't specify.

3) IS300 vs IS200?  An older thread here asked the question whether their radiators were the same.  The answers were not clear:  one said the "fan cowling" was different (but this isn't part of the radiator....!).  Another said the Lexus parts list had the same number for both.  For the IS300 I have found 16400-46560 and 16400-46561, and also 16400-46720 and 46721.  Can anyone confirm definitely whether an IS300-auto radiator and an IS200-auto radiator are in fact the same? This matters because there are lots of listings on eBay and from parts-suppliers for IS200 rads (a much bigger market) and few of them indicate whether the item will fit an IS300 (which are much scarcer...).  If they are the same, I can browse for an IS200 one, as there are many more to choose from!

4) Alternative suppliers and part nos.  The range of brands and prices is huge.  Does anyone have a reliable cross-reference list? I believe Lexus OEM radiators are made by Denso.  Cost around £245 from a dealer. I have seen aftermarket items from Nissens (Danish) p/n 646924, cost £130-ish;  Koyo (Japanese, sold by Euro Car Parts) p/n 203820450 - not clear whether this fits both IS200 and IS300 - cost around £100.  Other makers include TYC p/n 2356, Spectra CU2356 - and there are others.  Has anyone had experience - good or bad - of particular aftermarket brands? I don't want to get a replacement which doesn't last.... but £245 for an OEM item seems unreasonable.

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I'm bumping this up in the hope that it might inspire a reply or comment from LOC technical gurus, and because I've had PMs from other forum members asking if I have got any more information yet.  I'm still wondering whether an IS200 and IS300 radiator are actually the same - or at least interchangeable.

Any responses would be welcome!

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