1st question: Look here. 2nd question: '04 Pescarolo. And look here for a write-up about these type of cars.
Just so you know, you will want to use the Search Function, and if you couldn't find the answer to your question, then post your question in the correct forum.
Well Lloyd, if you're a good driver and want spec points, use the Mazda 787B. At 951 HP, R1 tires, and 200kg ballest, it's reasonably easy for a good driver to win each race and get 127 spec points per race. The 3rd and 7th race I had difficulty, and just used R3 tires and no ballast, but only got 10 pts each on those two races.
I really don't know what you mean by best. that depends on your goals. I only tried the 787B because it is my personal favorite from GT3.