How I see low hp engines, have what I call free hp, what the long block can make with just a 4bbl cam and headers, basically what's possible with the stock heads and cr. We know magnum heads and cr are able to make at least 400 hp which is a 100 hp over what a stock cammed magnum with 4bbl and headers which is about 20 hp over stock intake and exhaust.
The cam he uses is about half of what a 400 hp magnum uses, plus stock cam are so weak doesn't take much to be a big improvement. Even stock duration on a tighter lsa with more lift, probably be a decent improvement.