I recently purchased a chevy one ton step van, it looks like a fed ex truck. I'm wanting put seats in the back and make it look like a fancy stretch limo. I'm going to put a bunch of lights in and and put in a sound system, a computer and a tv. I am not sure how to power everything since I will probably run everything for possibly up to 3 or 4 hours without the van running.. I think the best option would be to buy battery isolator, im curious if i will need a new alternator. Any suggestions?