The only thing I can find about a 2743 model is the Thinkpad SL400. Is that your correct model? If so, the SL400 2743 uses an SATA hdd. The T42 uses an IDE drive. Either way, it doesn't matter what laptop you had. You just need to know what kind of hdd's you have. If the drives have pins as connectors, they're IDE. If the drives have slot type connectors, they're SATA.
You should be able to find enough info on any laptop for it to specify which type of drive it takes. As long as it takes the same type of drive as the ones you have (SATA or IDE), then it'll work in the laptop you choose to get from ebay.