I have HS965MG's in my current MoJo but I'm favoring the Savox line for future builds. They have the smoothest gearsets I've seen.

I have some of the 125oz [link=http://www.savoxusa.com/Savox_SC1251MG_Digital_Servo_p/savsc1251mg.htm]Savox 1251MG's[/link] for my future 40 size profiles.
And these 166oz [link=http://www.savoxusa.com/Savox_SC1258TG_Digital_Servo_p/savsc1258tg.htm]Savox 1258TG's[/link] for my Primo 60.
The Savox servos use a 25T Futaba spline so servo horns are easy to get in the right size.

The ST90 is not a great 3D engine but might work OK. Saito 100 and a 15x6 is much preferred for the MoJo 60.
The 140YS is a great engine for the MoJo65. Keep it.