upgrading alt.

I just cannot image needing that much power generated in a passenger vehicle. Pop up Ferris Wheel packed in the trunk ? If you truly have built a 73 Dodge Carnival you have forfeited horse power and fuel mileage in the process.
Consider all the other passenger vehicles around you. Focus on minivan accessory load, front and rear air, front and rear wipers, everything you have and more. And you need twice the power supply that they have onboard ? To unblow my mind, I would need to hear your jukebox from the top of that Ferris Wheel. LOL Good luck though