Driveshaft length

Im not sure what came from the factory. The service manual only specifies the engine and not the transmission. Example: 318 with auto trans .... 49.27"
it say's what trans came with what engine, and what rear end. call a drive shaft place close to you. ask them how they want it measured. then, if you have a shaft that fits, great. if you have one too long, have them cut it. too short, buy a new one. but you need to make sure what the yokes are too