Tricky question, but if you are serious about 'track' (drag racing?) work you amy wish to consider having two sets of wheels, one for the road, one for the track. Anyway, 15x7, or perhaps 15x8, will usually fit without modification, and allow you to use tyres with an aspect ratio of not less than 50. Less than 50 can make for a hard ride for no real advantage. Lots of things to consider - cost and availability of suitable tyres, car ride height, affect on gear ratios, speedo accuracy, wheel offset, etc. I have no knowledge of drag racing but have found tyre sizes around 205 to 225 X 55 to 60 X 15 to be good all round for street and race circuit work on my '77 model. Any wider than around 225 will usually require body modification, at least, particularly in the front.