Well, an engine itself isn't all wheel drive, or two wheel drive. It's the tranny and the drivetrain that determines that. The tranny that is mated up to the third generation 3S-GTE is all wheel drive though, and it will cost a lot of money to convert the car to all wheel drive. It involves buying a rear clip of a GT-Four, cutting and welding parts such as the rear floor, re-locating the gas tank, etc. It's a ton of work, and will cost you a lot of money. I'd guess that it'd cost you over $10,000 Canadian at least only for the AWD conversion.
As far as the price of the 3S-GTE clip, it varies, but expect to pay $2,500 or more for a quality clip from a reputable company. Also, they're in high demand and there aren't many wrecked ST205 Celicas, so they're very hard to find.
Also, the third generation 3S-GTE has 255 PS, which equals 251 horsepower.
Hope this helps.
And blkGT, the company that I'm having problems with is Storm Performance. In just a few minutes, I'm going to call the Better Business Bureau again. I've called and emailed Storm every single day for the last two weeks, but I've never recieved any replies.