Winter build

Ok so I am looking to build something stronger for my jetboat during the winter months. Right now I ran the numbers on my current engine and it comes up with either a 2 or 4bolt block with 049 heads. Block(361959)heads(353049)
Its a tired ol engine right about now. Im running a single 4165 Holley 800cfm doublepumper on a high rise Edelbrock dual plane intake. Not sure what cam it has in it. Using a Pertronix inside a Mallory. All is tucked under a compartment. Stealth is the way i like it.
It hooks up fine and ran pretty good up until lately.(tired valvetrain)
Not sure what hp im at but it turns 4700rpm max.
So Im looking to upgrade into something that will get me to 5500 or so rpm
I keep run across 454 hear and there and was wondering what blocks would be a good replacement. Im thinking that I can leave this engine as a spare and build another one. Im not sure if I need to go with a steel crank and 4 bolt and all. Or would it be more wise to invest in going roller with it or go with a small blower on it. Nitrous seem out of the question since I will be running it for long periods. Any suggestions as to a good donor or build specs?