The number of the transmission gives a bit of a clue as to the holding power. For instance: W4A31 is a NT Auto trans, W = AWD, 4 = speeds, A = Auto and 31 is the torque capacity. Whereas a Turbo AT is a W4A33. A 1.8L DSM Auto is F4A21. From what i've heard, a 2.0NT AT can probably hold decently with just bolt-ons, 14b, etc. After that it's probably going to be trouble. Kevin never had any power holding problems on his Turbo trans until the 11s, and even then it was only 1-2 clutches. So for a nice, near stock DD, it's probably ok. But, be aware the different years had different sensors and programming which can lead to a headache when swapping.
And the end clutches for ALL Mitsubishi Autos had issues. But, the replacement end clutch packs solved the problem and they can be changed still in the car.
Wiz