No one has mentioned that 3,300 is the dividing point. The porting offers no help below that point, either in torque or horsepower but does pick up a good amount above that. Where do you plan to spend the most time? Above or below 3,300? And how important is that extra power above 3,300 to your planned usage since there is no gain (actually a little loss) below that. That much low end grunt trying to push that heavy boat will be a major tire-fryer anyway, so would more of the same even be usable?

Why not just try the heads you have as they are to see how you like it? Would it be that big a deal for you to throw the extra coin at them later if you just had to have more? Also, if you wait and still wanted more, you would have a better feel whether you would want to just port the Eddies or move on to bigger, better heads.