The problem that I see is the throttle linkage. Right now you have a barrel throttle, when you go larger you get the slide throttle. On the t-maxx for example you have to add the post that switches the direction of the linkage. A minor mod, but one you cannot avoid. If you can add this post or something like it then I would look at the LRP engines. They have a reputation a good strong and reliable powerplants. But one thing to consider is that when you start getting stronger engines you may need to beef up the rest of the driveline, or risk twisting driveshafts, and shelling off gears.
Do not take this as a dont do it, just more of a tips thing. The other thing to consider is the exhaust. Currently you have the side exhaust, the larger engines have rear exhaust thus needing more room behind the engine. It can be done, just need a little more work. Shaun