The Baja is based on the Subaru Outback station wagon. It was not the first open bed unibody car truck from Subaru; the company made a car called the BRAT from 1978 until 1987.
There were only two engines sold with the Baja. The first was the standard 2.5 liter H4 making 165 horsepower. The upgrade was the turbocharged 2.5 liter H4 that made a much more impressive 210 horsepower. Many people feel that the turbocharged model should have been sold earlier on in the production cycle. With the weaker H4 boxer engine and the smaller size of the Baja, it had trouble selling against its larger and more powerful competition like the Chevy Avalanche. The Baja also came with some very weird color choices like bright yellow, and they failed to appear to the general truck-buying crowd.
Due to a surplus of inventory starting in 2006, many Baja models could still be bought new at dealerships as late as fall 2007. Although they did not sell well during their lifespan, the Baja still appeals to a unique niche of buyers who need the passenger space and the cargo room in the back.
If you are looking for a good deal on a used Subaru Baja, I suggest checking the listings on eBay or maybe even browsing your local craigslist. There are also lots of aftermarket parts on eBay.