I have friends/family with samurai's and it in not uncommon for them to break their zuk cases with the 1.3. I'm pretty sure a toy motor would make a bomb out of the zuk case in no time and even if it did hold up for a while it would be a big step backward in strength. Your best bet would be to gear your axles.
![My Two Cents :twocents:](https://board.marlincrawler.com/Smileys/marlin/twocents.gif)