I leave a long time, but now i buy a new ZXR 400 to use as my track bike.

I buy this slick Dunlop tyres.
120x70 frond
165x55 rear.
The problem is that the rear tyre is for 5.5 wheel rim.
Is a problem to use to our stock 4.5 rim?
Can i use a diferend rim from anyother ZX series bike.
Thanks
Andreas
Greece.