Other things that don't duplicate what's already been said:
- CNC prop
- AirTrakker video camera mount
- Spare tire for your trailer
- extra USB and 12v plugs all around the interior for stuff
- replace old engine box insulation to make it quieter and cool looking
- hard wire new trailer plug that goes direct to your tow car w/o adapter
- replacement boat LED instrument lights and running lights
- 12v heated blankets for windy days / cold passengers
- box anchor and anchor buddy
- refresh trailer bunk carpet
... and 2nd the items: Fresh Air Exhaust, Perfect Pass ...
I've got a 94 Maristar 225 - love your MC!