and for the 17.5 specifically:

86 40 1.02 2.15 4.43 1.84 46.85
86 41 1.02 2.10 4.32 1.89 48.02
86 42 1.03 2.05 4.22 1.94 49.19
86 43 1.04 2.00 4.12 1.98 50.36
86 44 1.05 1.95 4.02 2.03 51.53
86 45 1.05 1.91 3.93 2.07 52.70
86 46 1.06 1.87 3.85 2.12 53.87
86 47 1.07 1.83 3.77 2.17 55.05
86 48 1.08 1.79 3.69 2.21 56.22
86 49 1.09 1.76 3.61 2.26 57.39
86 50 1.09 1.72 3.54 2.31 58.56
86 51 1.10 1.69 3.47 2.35 59.73
86 52 1.11 1.65 3.40 2.40 60.90

Novak recommends no lower than a 3.4 and up to 3.7.
You can get the 86 tooth spur and 52 tooth pinion from Precision Racing Systems.