Operation Sarcastic Riot is a conversion pack for adapting DnD and OSR content to FIST.
The PDF is 17 pages, with clean, well organized, zine-y feeling layout. Pictures are provided throughout, and everything is easy to read.
Contents-wise, this is a detailed and thorough conversion kit. There's rules for adapting everything from AC/Armor to Choke/Morale. It can get a bit formulas-y, but all of the conversion is designed around working quickly and getting to the heart of the content. You don't need to know calculus to use it.
The tone of the writing is conversational and direct, and this really does a *lot* to keep the text approachable. Reading it feels like sitting down to chat with a friend, and there weren't any places where I felt confused or had to double back to check a mechanic.
There's a lot of supplemental material here as well, including new Traits, monsters, and a section at the end with very specific guidance on converting from a ton of different systems. It's extremely detailed and well-researched.
Overall, if you want to lean further into FIST's osr tendencies by using it to run actual osr, this is probably the definitive way to do it.