the following is from Boxford CSB Lathe

"the CSB was delivered complete, ready-to-run with a 1/3 h.p. motor for £105 - a total saving of some £16 : 5s : 0d. The simplified 8-speed drive had the motor bolted direct to the countershaft upright instead of on a separate, adjustable horizontal motor platform. With a single-pulley drive on motor and countershaft, and using backgear, the eight spindle speeds were: 38, 55, 87, 125, 200, 285, 450 and 650 r.p.m. By paying £3 : 10s : 0d extra the motor and countershaft could be fitted with 2-step pulleys when the speeds became: 38, 55, 75, 87, 110, 125, 175, 200, 250, 285, 400, 450, 570, 650, 900 and 1300 r.p.m. Unfortunately the makers neglected to mention the fact that in order to run on top speed a more powerful and expensive motor was required"

now you know what speeds you should have, you should be able to work out the pulley diameters needed