Seems like if we "think like the enlarging paper", a #47 should be fine. It peaks around the same wavelength as the #94 based on the numbers Mr Bill provided, although with a #47 the transmittance figures are much higher, peaking at 50%. The cuttoff around 490nm is about the same as a #47. The difference is the #47 cuts off at shorter wavelengths in the 380nm range. For the purposes of black and white enlarging paper it looks like the #47 is a good bet.