My '89 Van B250, full size has the 5.9 magnum in it. My '77 short van tradesman 100 has the 318 2bbl in it. The 318 gets about 1.5 mpg better, but it's in a much lighter van. While the 318 does as expected, and a good job, the heavier van with the 5.9 has so much more power.... well, it ran 15.8's consistently. That's almost as fast as a stock 5.0 fox body automatic in the same year... LOL