Should I get a large inverter?

Hey, I own a Ford Econoline/Ambulance.  There is an area in the back which is perfect to fit a 13"-15" television (not a car television....a regular television.).  I also want to add an Xbox and some blacklights.  My question applies to how to supply power to it.  Should I get a large inverter (and if so, how large and should i hook it up through the cigarette lighter or hard wire it?) or should I get some kind of alternate power source to power the things (I have no idea about any of this...I was wondering if this was possible, as to not drain my battery ) Any info would be greatly appreciated.  ~Vanbulance Driver~

You'll need a heavy-duty high output alternator, a large inverter (find out the total wattage or current rating for all teh equipment you intend to run) that is hard-wired and fused.  For use with the engine off, I recomend a gas-powered generator.Support the12volt.com

I was wondering how big of an alternator and invertor I would need.  I am thinking my alternator is already pretty big---I have two batteries, so it should be pretty big already right?  Also, I have switches that allow the batteries to be turned out without the car being started....I would mainly be using the T.V. and Xbox with the van off....just using the switches.  Would this be smart or would it completely wear down my battery?  (The TV would have approx. 65 Watts....the Xbox would be around 79 Watts (the watts that a PS2 uses..im guessing they are close) and the blacklights total would be at max.....80 Watts....) so total....prob.  250 Watts max?  What would be the best option?  Or, could you supply info on a gas-powered generator? Also, would adding a big alternator take down my gas mileage? It is already pretty low....so I'd like to avoid that if possible....Thanks for any help!~Vanbulance Driver~

I think it is a....7.9L engine...(not for sure on that...it is a 460 I know...however many Liters that is...) and it is not diesel...it is regular gas...I was wondering.... if I were to use it with the vehicle off for.....an hour or two at a time...would that be ok...would the alternator charge the battery back up the next time I ran it? Or would it cause a major problem?   Thanks for the help.~Vanbulance Driver~

that really depends on how this dual setup works, I'm not very educated on how ambulances work, but if there is one battery(with alt) that runs the van and starts it etc, and the other is for running any equipment in the van (on account of it being an ambulance and all) then you could run it all you like and it woul still start, but it wouldn't be that great on the battery to run it dead a lot.  see if you can find out how your batteries/alternators are set up.

oh, and a 460 is a 7.6L

sorry for all these little posts but another site said that the alts were dual 110's. not a huge difference but good to know.