Pull the distributor and check that the "dimple" in the drive gear is in line with the rotor tip. If it's 180 degrees out this will throw everything of half a tooth, and the distributor may not have enough rotational clearance to get the timing on the mark. Then, of course, "the fix" for this is to rotate all the wires one position and see if it will work. I've seen this one a dozen times, and even did it myself once. Indexing the dimple in line with the rotor tip is the proper way to assemble all Delco distributors. If your drive gear is 180 degrees out reinstall it properly, then make sure the wires are installed in the original cap positions. Most shop manual have a diagram.
Duke
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