Not to doubt you, but how have you determined that there is no spark produced? Is there no spark, or is there no spark getting to the plugs? Has the van been on a scope? If there is truely no spark, then it is very likely a primary-side problem. Things such as bad module, bad pick-up, no power to module, etc. A tie to the computer (if it has one) should not be a concern at cranking speed, since the module will trigger internally until it's running. I think it switches around 600rpm, but it's been a long time. Doesn't rule if out, but moves it down the list. To test for a functioning primary side, you could plug a tach into the tach connector on the HEI. If it moves, you've eliminated the entire primary side. If it doesn't, you know where to start. If the primary side is working, move on to the coil. A scope is the safest way to see if it is firing. Let's assume the coil is working for now. Have you pulled a wire to check for a spark? If so, don't do it again. If not, don't do it! The reason is that on HEI systems, the spark WILL find a ground. With the wire pulled it may arc through the rotor to the distributor (This happens A LOT. Look for a burn mark on the rotor bottom) It can also carbon track in several different places inside the cap...none of which are good. 10 volts during cranking is fine. Now for the "insulting" questions... There is a wire or metal strap that grounds the coil. It's the middle prong on the power connector. Did you put it in place? Did you put the new button in the cap correctly? (button first, rubber ring second) Even pros oops this now and then. Is the distributor turning? Sorry, but gotta cover all the bases.
I would suggest a trip to the nearest scope if the primary works. It will likely cost less than throwing parts at it, and saves a lot of time. If you have more information, please submit it.