I'm not a great expert of all this confusing wheel offset, tyre size but they might fit.
While thinking about this I recall noticing that the tyres fitted to the 18" wheels 360s wear have rather big sidewalls....not even comparable to the extreme low profiles seen on most GTRs. This is most probably due to the settings Ferrari has decided on, to mentain a good comfortable ride and great handling. But you might weant to check if this would compromise your R33s handling...ie tyre wall flexing during hard cornering.
I suppose it is possible but you would have to be very careful. i would want to consider the following:
1, are modena wheels 5 stud on a pcd of 114.3mm...if they are not this exactly then they will never fit.
2, if yes, you must determine the offset for the wheels. i'm not sure exactly what the correct offset for a r33 is, but since its is derrived from the 32 suspension i would guess it is quite low (20mm). skylines have an usually low offset. Ferrari wheel normally have a high offset (40-60mm) in order to maximise the wishbone length. it may be possible to build some custom spacers to correct this.
3, the front and rear ferrari wheel widths are differnt which means you will have to be very careful with the tyres you choose. the rolling circumfernce must be matched. if not you wil confuse the 4wd system in the skyline.
there is bound to be some other stuuf i missed, but those are the main points i think. personally...not worth the hassel. anyway good luck
Thanks everyone for the advice. My GTR is not with me right now, that's why I could not try the wheels out. However, if it is true that the offset is not the same and the front and rear width are different, I would not fit those wheels. I'd fitted tyres with different sizes on the front and rear before and the Attessa just went completely berserk! It's a pity really, because I really like the Modena's wheels. Have a look.