The Picco .26 red dot I know of is a direct drop in replacement for a Traxxas engine. The Traxxas engine is a small block, the Picco is a mid block. It has a special mount but you don't need anything to install it but drivetrain upgrades are recommended. That engine has been discontinued for years though. Big block engines on the other hand are longer and require a special mount among other things. Putting a big block in a Revo is a complicated conversion with lots of variables and lots of drivetrain upgrades are required. Honestly if you want that much power you're better off with a 1/8 truggy that's designed for that kind of power to begin with.

There are really only 3 easy engine options. Another 3.3 engine. O.S. .21 drop in replacement engine or Novarossi also has a drop in replacement. Personally I'd go with the OS as they're very easy engines to live with, wide tuning window, hold a tune nicely, just easy. The Novarossi will probably make a little more power up top but you'll be fiddling with the needles a bit more. Drop in replacement means everything Traxxas bolts right up including the EZ Start.