Easy, 95Dawg. If you ever read Shibumi, by Travanian, you would know you only kick the side of Volvos.
On a more serious note, if you have spark to the center of the distributor, and none to the plug wires, you have pretty much isolated where the fault lies. I don't know what's inside your distributor, but my MKIII has a very large rotor that makes contact with the tits that lead through the cap to the plug wires. That part is almost fool proof, and you already know you have no spark there. So backtracking, there is a spring-loaded contact in the middle of the cap, which conducts current from the HT lead to the rotor. This contact can get pushed up into the cap, and the spring sticks. If you can't push the pin up and have it pop back out, this could be the trouble. It has to make contact with the center of the rotor.
However, it could be that the distributor body has gone bad, not the cap. There are electronics inside the distributor that I do not think are replaceable. You may need to buy a distributor and put it in.
You may want to put this question on the MKIV list also.
I think you are almost there. Keep the faith.