Here's where the difference comes in between a cover letter and a letter of intent. With a cover letter, you likely already have a solid idea of what the job opportunity is, and how to position yourself for it. With a letter of intent, you have to make a slightly trickier balance—positioning yourself as qualified for a job that may not be clear yet. To do that, align your self talk around the company or the industry, making sure to highlight your skills and achievements that would make you a good fit for the company. You can also be specific about your level and experience. For example, you should make it clear that you're looking for a manager-level position if you don't want to be considered for more junior or entry-level roles.
Without job-level specifics, it can be tempting to get stuck in an "I'm awesome" loop without giving enough specifics. If you have a general idea of what job groove you'd be seeking at this particular company, build your letter body around that. If you're truly just trying to get a foot in the door at a company, you can use clues from your research about the company. What does their website say about their mission and priorities? What do current and past employees say about the company in online chatter? Even without specifics, you can cobble together a pretty good idea of what the company is seeking in potential employees. Sell your skills and experience points that are special to you, and especially relevant to your industry.