summits base 350 is like $1400, has 265 horse and a warranty. it is also a genuine goodwrench 350, which makes me feel better, just a thought.
if you want more horse than that i think that it it easier to just buy a crate motor that is what you want. once you factor in the time, money, sweat, blood, time, time, time that it takes to rebuild an old motor it is usually better (in my experience) to just buy a good crate motor. if you are going the origional style way then i would stick to what builder said, a 283 is not a hp monster unless you spend tons of cash, and then you may as well buy a 350 and go to town on it. just my two cents.