I'm not sure what the concern is over the valving being "different". The anti-drainback valve is not a complicated item. It is just a one-way valve. Its sole purpose is to prevent the oil from draining back (in the reverse direction from the oil flow when the engine is running) from the galleries past the filter and back out into the oil pan. That's all. The design doesn't matter - there are only two stati for an anti-drainback valve: either it works, or it doesn't.
I cannot believe the '00s have a distinct part number from the '99s. Everything about the oil delivery system is the same, most notably the physical mounting to the block. A 3310 will work fine on the '00- RS.
As for bigger filters being closer to the header... A lot of Hondas and Nissans have the filter on the back of the engine, tucked up above exhaust parts and below the intake manifold, where there will be no airflow whatsoever. The filter on the EJ25 hangs down into moving air. Still, consider that you can hold your hand 3" away from the exhaust primaries when the engine is hot and feel warmth. On the other hand, if you touch the hot engine oil it will burn you. I REALLY doubt that a filter which closes the gap with the exhaust by .25" would be measurably hotter on one side than the other, because the radiant heat from the exhaust is a drop in the bucket compared to the heat of the oil. But even if it were, the overall temp would still be lower due to a larger surface area exposed to the air.
That said, I think a 3" filter is plenty large in diameter. I would indeed be interested if anyone knows of a quality filter with the correct threads and gasket diameter which is 3.5" long.