Personally, I wouldn't touch a car that's been molested that much.. but that's just me.
CT26 turbo is what is supposed to have come on these cars, but not all CT26s were the same. Later revisions that ended up on the Celica-Supras obviously were a little better than what should be on the ST165 all-trac from factory.
He's got a bunch of aftermarket stuff under the hood like silicone couplers, manifold and wastegate, blowoff, I'm suspecting a possible modified OE AFM(which is a big no-no with these). If the car runs, I'm curious what type of manangement it has, if at all. If it's a piggyback style, don't touch it. It's probably been beat on, so I'd be very careful getting into something like this with that many miles.
Also, not mentioned are the Celica wheels, not original to this car.