IMHO the frame connectors are FIRST. You will absolutely not believe how much they stiffen up your car. Then I'd worry about the motor mounts. I think you may have the cart ahead of the HORSE (No pun intended!
) Motor mounts won't twist the frame because you have no sub connectors, it's the other way around. Put the sub frames in to stiffen the car, then put the motor mounts in to hold that HP down to your stiff chassis bro!