heres the deal..looking for a mild 500hp in a 468 bbc i have choice of running 2 heads either the 781 casting or a closed chambered 290 cast. i hear the 781 is a decent flowing head etc etc,, but a friend of mine has some 290 castings sitting around i can get cheap. whats the pros and cons here....??? any professional motor head advice would be greatly appreciated. should i hold out and wait for these 781 castings to put money into them, or should i grab the 290 casts and punch them out for this build.i wanna stick with a pump gas engine..91-octane, so yeild around a 10.1 or so compression, or as high as i can get and still run pump gas. im building a 18ft 77 tahiti, i dont plan on going to any races thats for sure, itll be a show and cruise boat with the 500hp im after.