I plan on purchasing JDM Recaro seats for my 98 ITR. Ive researched on it, and from certain websites Ive found a JDM armrest eliminator for sale to work with the Recaro's. Is this JDM 'eliminator' a required piece for the Recaro's to fit properly using my stock USDM seatbelts? I ask because I plan on purchasing the seats though I would like to keep the armrest if I can, and that my friend has a GSR with similar seats installed and to make them fit (while keeping the armrest) he couldnt use his stock seatbelts.

you could TRY to wedge the seats in but it will be a tight squeeze between the armrest and seat sides. the "eliminator" will make space, but you'll lose storage, and an armrest.

You do not have to lose your storage space. I felt the same as you do in not wanting to get rid of the stock armrest. I do admit it is a bit of a tight fit but it works for me. Good luck.