Yea, it's different for different markets, but I remember for the US we only had RA64 and RA65 and the difference was SRA vs IRS I thought.
Edit: so what I'm getting at is if it is possibly a late production 82 sold as an 83 with a SRA and fender flares like the 82 GT-"Sport" was, since I think that was also a RA64. If he reports back about his rear suspension that would be the definitive.