it will not. the wheel wells will not be centered. you can cut it down, but it won't be longer i don't think. sleepyspeed and roger26i have both done it. find their project threads. to actually extend the truck, you'll have to stretch the frame.
standard cab long bed if your gonna extend the fram..keep in mind you wil need to have an extended drive line mad extend brake lines ebrake line and wireing
yeah, what todd said. seems like a lot of work involved, but from what i've seen, very worth it. i've seen one on here.. i think it was 19 ft. it was an ex-cab longbed. very sweet.