Sorry been out of town a few days. Just got back. Don't know if it will be an EXACT drop in, but I do know it won't be hard. I don't think its big enough for the Gecko, I would recommend atleast a 380 size brushless for that. My 400 Feigao is a little too much for it.
Yes the Mamba should hold up fine with the 280, but probably not the 380.