Need help

[WILLOW CREEKER]

I have a new 2007 ranger. It came with a 520c / gps in the dash networked to the same unit in the front of the boat.

The dash unit broke, and is being replaced by my dealer, but I want a bigger unity at the consul.

My question is how big of a unit can I put in the existing hole on the steering councel, so I don't have to drill any holes on top of dash to mount the seperate unit.

Also how do I hold the unit in place. The existing unit didn't have anything but a gasket holding it in place, just pushed into the hole.

Also will the new unit be able to use the existing wires so I don't have to run any new ones.

Thank you