AI Models that will let me upload a large number of lines of code?

I run a small web design studio. I’d like to find some kind of way to pass an entire site template (which might be thousands of lines of HTML) and have the AI replace all of the text.

I don’t need real “copy,” rather just replace the Lorem Ipsum with something that is at least somewhat coherent. The purpose would be to demo site designs to clients, with the actual copy being written by a human later in the process.

The problem is that ChatGPT will simply not accept that many characters…

Are there any models that allow a much greater number of data to be fed in? Are there any self-hosted models worth considering?

Gemini 1.5 has 1 million context, and for a local option Introducing Jamba: AI21's Groundbreaking SSM-Transformer Model jamba has 256K