would it be efficient to gear 2 393’s with 3 12 tooth gears together?
Yes. 8701 has something similar except six motors.
That sounds fine, and is a common way to have two motors drive a single axle. Make sure to make a solid gearbox so that your gears don’t slide or tilt.
I like how your designing your bot by asking questions here. Its a good idea, why design something then find out it doesn’t work?
exactly i mean a lot of you have tried this stuff so why not ask it? 
cant wait for my next robot reveal!
Oh boy oh boy, us neither.
By the way, yes. Our B team is doing that right now.
You could also just use two thirty six tooth gears.
thats what i did last night in my inventor sketch