A little more information about your intentions with the vehicle would help. Are you planning to use all that HP regularly, or is the HP number just a "general information" question? The small blocks we ran on the round track were in the 600+ HP range, and we used all of it often, like 3-4 times a lap on a 1/4 mile oval track. It was not uncommon to lift the left front wheel several inches off the track while coming off a turn, even with a very rigid roll cage and frame. Very few street machines ever see that kind of stress, even with some energetic stoplight launches.

If you're going to be drag racing on a routine basis, build the chassis with that in mind, maybe with the cross brace you mentioned. Otherwise, just be sure everything you add to the frame is square and straight, with a minimum of welding involved. Good luck!
Jerry

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