4 cylinder V8 ?!

[USMC302]

OK here's the deal, changed one blown head gasket. New ignition wires, new sparkplugs. 1,2,8,6 cylinders aren't firing. When the wires are removed from the dist cap, we have spark from the terminals. When we put the wires back on, there is no spark. We take the spark plug out and leave the wire on the plug, and it fires when out of the cylinder... Car will not run off of all 8, just four. We are going off of the correct firing order and everything. Fuel pressure is set to 32lbs, timing @ 12 degrees advanced. Stock everything except fuel pressure reg (BBK), pulleys, and exhaust. Before yall ask how do I know that the spark plug isn't firing when it is in the cylinder, we were grounding each one out by putting a test light on the negative battery terminal and stabbing the top of each dist terminal through the boot. Theoreticall, the idle will go down and there will be a noticable difference when the plug is grounded out. 1,2,8,6 did not do crap. Please help