Since you're mentioning a 10 under the AB, sounds like you might have a 64 or most likely a 65 Dart, Valiant or Barracuda. If you have a 65, a 10 under the AB would indicate it originally came with a 170, a 20 would mean the 225, a 30 would be a 273 2 barrel and a 31 is the 273 4 barrel.
Visually, a really short (about an inch or so) water pump by-pass hose is a 170, longer 2 to 3 inches a 225 or 198 since they share the same block/head. The 198 was used from 70 to 74. Hope this helps.