[Kalanco]

If you have any luggage racks, lose them.

I have a very small, likely aerodynamically designed, low rack of sorts. I don't know what to do with it or where I'd put it if I took it off. I do admit to only using it once, though.

You can reduce frontal area by slamming the van. Your van is essentially built on a c-10 chassis and I thing both the front and rear ends are the same. There are plenty of slam kits available for C-10s of your vintage. Between 3 and 5 inches of slam leaves you with a roadable vehicle. I reduced my F350 4” in front and 6” in back and gained 1.0 MPG.

I'm not sure how accurate that statement is. I have a G25 van, not a C-##. Nevertheless, I'm sure they do make coil spring lowering kits, and I've seen a leaf spring lowering kit.

Lose the 235s. Get 195s or 185s Get LRR tires. Air them up rock hard. I run 25% over the sidewall pressure rating. Get flat hub caps or Mooneyes. Follow up with fender skirts.

I'm a bit afraid of making the tires much smaller than the stock 225's(I thought larger tires reduced rpm's at a given speed?), as a lot of places in town have some pretty severe dips and bumps(I scrapped the back of my trailer hitch thing driving out of my workplace 2 nights ago). Also, 25% over the sidewall pressure rating? I could see that in a car, but when each tire is holding 1250 lbs of weight?

If you want real MPG, you’ll eventually have to do something with the back of your vehicle. The more you can reduce the trailing area the better but there is one proviso, you cannot make the reduction too sudden or you will cause the boundary layer to separate. My fastback cover is too steep at 17 degrees. A better angle is 12 to 14 degrees. That is a 1 in 5 slope. A 1 in 4 is fourteen degrees. The ultimate boattail is basjoos’ but his car is a lot smaller. You’d wind up with a boattail twenty feet long. Best compromise is to make a tail fairing that is 12 inches long and tapers in 3 inches from each side, top and bottom. Make sure the transition is smooth and gentle.

Do you have a picture? If I had one, I could probably wrap my mind around this concept a bit better, although this doesn't factor in my rear doors.

Mechanical stuff

I think the largest engine they put into this van was a 5.7L(350). They might have put a 6.2, but the van engine bay is pretty cramped as it is, I don't know how they would have made it fit. Also, while it only generates 250 ft-lbs of torque, it makes about 210 horsepower, far more than your 125hp estimate.

Final ratio, is actually a 4.1. The lowest I'd be willing to go would be a 3.08, as I'd expect a 2.73 to take me about 25 seconds to get to 60.