Bolt it down very carefully. Have a beer and admire it for 5-10 minutes, then take it off and replace it with a Holley Street Dominator!

Just kidding, the RPM is a great all around manifold on a 440. There are a few runners in the lower plenum that I massage and I tend to run a long strip of emory through all of the inside and outside runner walls and to the plenum to remove any casting burrs inside. You can do some deep porting (which includes enlarging the plenum halves) but for the effort it's much easier to work on (and yield more out of) an SD. After running the Indy 2D (ported to full Max Wedge) I think it's a better power and torque producer than both of them but it's difficult to get your hands on a non core-shifted casting.

For a 440 the RPM is as close as you can get to a no-brainer, it will work very well right out of the box with a 750-850 double Pumper. And unlike the SD , the RPM even works great on an otherwise stock motor with highway gears and stock stall. 440's are easy torque producers, it's amazing they ran as well as they did with the stock manifold with all of its Acute runner angles.