An example from Commonia = [http://opengeofiction.net/#map=18/17.24328/140.42537]
As far as I know in New York City the blocks are 60 to 240 m. If you calculate as minimum 1) street a, right side driving lane 3 m, 2) parking lane 2 m, 3) footway 3 m, 4) house at street a 12 m, 5) inner block 10 m, 6) house at street b 12 m, 7) footway 3 m, 8) parking lane 2 m and 9) street b, left side driving lane 3 m = then you get 50 m. This is the absolute minimum for reasonable buildings inside of the blocks.
If you will do a good work for the inhabitants of your town - give them more room.