I guess we really need to know what age or vehicle the wiring harness is from. Does the HEI have a big red wire with a factory style connector on it or is it homemade and adapted to fit the harness. I presume it has a new column with a key start system so to diagnose the problem, you can test the fuse box and find a 12 volt power source that's hot while cranking and plug that into your distributor. If it starts normally, it's probably a wiring problem which I suspect since it happened all of a sudden. Regardless, I think we need some more info on what's in the truck,
Scott
