I have a 1977 Safari (23 foot Airstream). My Univolt has died. I am thinking of purchasing a Progressive Dynamics PD9100 Inteli-power Converter. My question is - what size do I need for my 1977 23 foot Safari? They come from 30 AMP to 80 AMP. I want to order the right size for my Airstream. Thanks in advance. Dan Osterhout WBCCI #4495