Thats GT-One not GT1 the toyota never has been GT1 class, It started life in its infancy in the early 90s model number
Toyota TS010 and was a full blown Group C later in the late 90s the
Toyota GT-One TS020 evolved as an LMP. Totally different beast to the GT class.
http://en.wikipedia.org/wiki/Toyota_TS010
As far as I remember, during the end of 1990 rules allowed manufacters to build extreme GT race cars which resembled prototypes in the shapes thanks to some "holes" in these rules. During the 24 hours of le mans of 1998, many manufacters presented very extreme GT1 cars, such as Toyota GT-One TS020, Nissan R390 GT1, Porsche 911 GT-One EVO and Mercedes Benz CLK GTR, all of them very far from the real concept of GT1.
But the Toyota was the last one to join the party, in fact it has almost nothing of a GT1 car.
A long tail and some other adjustments were added to the Mclaren F1 GTR to improve downforce, but the car was still based on the old 95' GT model, in fact it was no more competitive. The Mercedes was built under FIA GT rules so it couldn't be too much similar to a prototype. The Nissan was based on the 97' model, just more reliable and with better downforce. The Porsche changed almost everything in his old 911 to reach better performances. The last remaining, the Toyota, simply built a totally new car, the GT-one, which was extreme in every way.
In 1999 rules changed again, GT1 class changed into GTS and only allowed "true" GT cars to joining, and all previous GT1 cars moved towards new LM Prototype class. This allowed manufacters to improve their cars even more than before. In this year, and only in this one, the Gt-One ran under LMP rules. Nissan and Mercedes were forced to present brand new cars.
