[nvrenuf]

Are you also converting from sbc to bbc? If so I don't think that's a realistic number.

I think it's very do-able to get 600 hp for $5k but if your converting there will be a lot of extra parts that will eat in to that same budget. Things like headers (and exhaust mods), a big carb, adequate fuel pump (and plumbing mods), radiator, motor mounts, parts to finish the accessory brackets, etc.. will all kill you on unplanned expenses.