When these cars were classed, 13x6 wheels were pretty plentiful. Not OEM wheels, but probably half a dozen aftermarket brands (Rial, Ronal, Enkei, Borbet, BBS, Speedline, etc.), plus the traditional 'race' brands (Revolution, Panasport, etc.) available. Now, it's just the 'race' brands.

Unfortunately, if you want to run the 225/50/13 Hoosiers, you'll need a 6" wheel (which is really still too narrow). You can get away w/ the 185/60/13 on a 5.5" wheel w/o any problem at all. You'll give up some lateral grip, but you should cut down on straight-line drag. And, you should be able to get sets of used 13x5.5" wheels for $50-$100. You won't get one Panasport, Revolution, etc. for that.

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MARRS #25 ITB Rabbit GTI
SCCA 279608