I like to put 14" or 15" Maybe 16"

I believe that 14" pickup rims will work, might be 15 and 16 also but remember it may throw your mechanics of the way the van handles off and it will definitely throw the speedometer off.    

How about bright, chome 20 inchers with spinners. :) Rad

Rims with a 4.5 X 5 bolt circle will bolt up. Inset should be that used on rear-drives. On Fords, that's many of their rear-drive cars. Any Ranger, Bronco 2, or early Explorer rim will fit. 89 up TBirds and Cougars, as well as 79 up Crown Vics and Grand Marquis. 60s and early 70s 5-lug Mustang, Torino, Montego, Galaxie, etc. all use the 4.5 circle. I think some 70s Chryslers and AMCs may also have used the 4.5 bolt circle. Some F-100/150 may fit. I think later ones have 6 lugs, however. If you look, you can find plenty of used wheels to bolt up. Come to think of it, it might be nice to find an old set of Cragar S/Ss or Magnum 500s. Some old Mustanger ought to have some.   Don't try to mount rims from a front drive (Taurus), wrong inset and bolt circle. Fox bodies (Fairmont, 80s Mustang, 80-88 TBird) normally used 4 lug wheels, so they're out.   If you go up to a 15 inch or larger, if you want the speedo to still be accurate, you'll need to mount lower profile tires. Generally, if your Aerostar has 205/75/14 mounted, and you go to a 6x15 rim, try mounting 215/65/15 or 225/60/15. With 16s or 17s, you will be into 55, 50, or 45 series tires to maintain the same diameter (to maintain speedo accuracy and to fit the wells). Tires with that low a profile handle very well, but don't handle truckish loads well. 6" wide is as wide as you can go without making body modifications. If you go larger in profile and modify things to fit, be advised that Ford does have other speedo gears, for earlier models that use a gear for the speedo, to accomodate the new size.

Am I the only one on earth that think the spinners are stupid and ugly looking? (on any vehicle, including Aerostars and Windstars)   Seriously, if you intend to haul loads in your van, don't go over 15-16 inches. Tires below 60 series don't handle heavy loads well.

Far from it. The first time I saw a Cadillac Escalade sporting a set of 26" pimp spinner rims I about laughed myself silly. When I saw a H2 sporting an even bigger set of wheel bling and low profile tires I did. Cracks me up. Rad