305 heads on a 350

looking for some imput im not a mechanic in anyway but im some what nolegable.i race in a small stock enduro class(circle track) out on long island and i here guys talking about puting 305 heads on a 350 and you can get as much as 100 HP(wich is alittle unbelivable)but what dose it do. i heard better compresion and bigger valves.every now and then they will tease you with a little article in a magazine but they dont explane it.
i just want to no whats the difference

no horsepower gain to really speak of.. with the right cam, intake and exhaust, it makes for a nice low end torque truck motor with smaller valves, combustion chambers, and higher compression. 305 heads are usually 58cc, with small valves..

The "601" casting (late '70s, early '80s) 305 HO head is the one they're speaking of. It has the 58 CC chambers mentioned in the previous post. It also has 1.84" intake valves (as opposed to 1.72"). The heads flow pretty well, all things considered. It's an old hotrodder's "trick", like using 283 "Power Pack" heads on 327. A pair of World Products "Sportsman" heads would be better, and probably still legal. Not cheaper, though.

I seen an article I have been looking for that disscussed this.... it said the compression would be to high using 305 heads...cant seem to find it tho.
I thought it was on popular hotrod or something like that. Showed how to mod the head to work also
this sound true?