I have sweet 1987 rogers daycruiser that is a great boat for my family. The previous owner installed a 454 ho/king cobra (cone style) like the bravo. I rebuilt the drive last year. I need to get about 15 more mph out of the boat. It will go 60 all day and I have had it up to about 68 running light (fuel, icechest, ect.,) I get about 5400 rpm. What is the best bang for my buck? I wish it was a bravo....but i'm stuck with the king cobra....any formula's or info would be great....thanks