you're gonna find the Axial .28 is gonna be a small project to put in a Revo,if you can get the engine to fit with that shaft length configuration..you're gonna have to purchase a manifold and engine mount for it,also possibly a flywheel with clutch and clutchbell also ..... you're gonna run into problems getting the throttle to open up fully,plus you're not gonna be able to utilize the ez-starter...To beef it up you're gonna need Traxxas steel cvd shafts and center shafts too,plus a steel hardened spur gear and hardened clutch bell
In my Revo I have the Sirio .27....It was a direct mid-block upgrade kit for the Revo that comes with exhaust manifold , engine mount and still gives the ability to still use the EZ starter...The throttle fully opening was still an issue but easily fixed with a servo swap...Good Luck with your choice