[ChopStix]

If you block the top half of your grill like your picture shows, you are on the fast track to a fried HEI ignition module. There's not enough cooling in Astro van's engine cavity's for blocking the whole top half like that. There's numerous posts both on this forum and on the Astro forums about this distributor overheating problem. You would be wise to carry an extra module with you for when it dies. I run no grill block for this exact reason.

Also there's a temp sensor on most years located on the side of the radiator. I would advise against blocking it as well. Its claimed online that blocking it makes your engine run extra rich.

Hope this helps.

edit:

PS - Write down your vin and call a dealer as some years have recalls on the stock computers. Which on mine was a note worthy MPG gain.