I went and talk to my local exhaust shop about 5inch stacks on my 98. He said he has done many like this. This is the way he told me, First get a piece of plate metal, something like 6x10x 1/4thick or so, then cut a 3inch hole in the center, then weld the stack to the plate, then on the other side weld a 3inch short piece of exhaust pipe. then cut the holes in bed and bolt the stacks the bed. now under the truck, I'm going to running 4-inch down pipe and 4-inch back to the bed. then he has a y-pipe that the 4inch goes into and two 3inch comes out. then run each 3-inch to each stack and throw some flex pipe inbetween somewhere for flex. He said by useing 3-inch it will clear the fuel tank. I thought i was a bad idea going from 4 to 3, but he said i'm going from 4 to two 3's, witch is actually like going to 6inch. He said all the one's he's done sound GREAT, What do you guys think, it would look pretty clean inside the bed??