Ideal front wheel backspacing for a GENI

[bucks69]

Hey guys if you were building your "ideal" road/street racer what would be the backspacing you would want on the front with a 17"x10" wheel And also an 18"X10" wheel? Also to go a little further what would the rear backspacing be for a 18"x12 and a 19"x12"? This is assuming you were going with a custom frame and could go with whatever size and backspacing you want. This is for a regularly driven street car if that helps any. Also please elaborate a little about your decisions please. Thanks in advance.