My guess would be in the 500-600 range. Basing that opinion on the conservative fuel setup. I've got a walbro 255 and 750cc injectors on my 4 cylinder 400hp car. you could probably hit 700+ with those parts listed, but i would assume someone building a 700+ hp car would have more fuel system than they needed and have it running low duty cycle vs peaking the performance.
anyways, you asked for a guess, i offered one. shooting in the dark, lot of variables.