text-davinci-003 was instruct-trained gpt-3 gpt-3.5-turbo-instruct is its instructGPT replacement
davinci was a GPT-3 base model that is a predictive completions engine davinci-002 is the next version (likely based on 3.5 scaling)
In the following forum link, an example of what it takes to get the newest base model to form cohesive responses if you don’t train by fine-tune: train by multishot input, placing the AI into a state as if it was still completing a “document”.