Welcome to ATP, and hope we can help!
First thing, please do think about the 8ft. square bed - you will need to step into the bed to get at the plants in the middle. This will compress your soil, and really the whole purpose of a raised bed other than to have better drainage and not have to bend over is to have better soil, with air in it. You might consider making two narrower beds with a pathway in between.
Also when you fill it up be sure to overfill it - mound it up - as much as possible because the new soil will settle a lot! Tomatoes like rich, deep soil. Most people just level it with the top of the bed because it looks nice and neat, then wonder in a month why there's only 5in. of soil in their 8in high bed. Don't pack it, let it settle on its own, though.
If you're starting from seed, (start soon, its getting time to plant out transplants!) there are some 'heat tolerant' types like Solar Flare and Heatwave that will continue bearing further into the hot weather. For fantastic flavor, I've been really enjoying Mountain Magic and Momotaro. All these are available from my favorite source for tomato seeds, Tomato Grower's Supply. A lot of the cherry, and 'grape' tomatoes also tolerate the heat longer than the big fruited types.
Um, forgive me but although we are very casual around here, to type in all caps, that's kind of like shouting in a conversation.
