if I can keep my foot out of it, i get over 20 unloaded with the 12 valve.
when you reference needing a 6 foot bed to fit in your driveway, is your driveway really that small? Just curious. I'm usually a fan of buy what you can afford at cash value and look into parts to understand what it costs to maintain. I'm not particularly a Ford guy, but if the right deal came along, you'd see me driving in one.
Also, please consider how much you think you'll be towing vs. not towing. I was looking hard at 6.0L Chevy gassers, but I managed to get my 12 valve for less than half what I could find a decent 6.0 for.