Well, then see if maybe this scenario sounds familiar:
When timing the cam on the engine, the crank needs to be turned in a clockwise direction (as viewed from the big nut on the spark advancer), and NOT backed up. Backing up in the CCW direction causes 2 things: a.) it bends the long, thin stud that holds the spark advancer in place, changing the spark gap and timing requirements in the process and b.) tends to make the dowel receiving hole in the crankshaft oval, which then lets the sprak advancer tilt on this newly-bent shaft. This causes the timing of 1-4 to advance quite a bit, while making the timing on 2-3 "jitter" or require less gap than the 1-4 side, to make it meet the marks.
If you suspect this, remove the advancer and put a dial indicator on the shaft near the threads, check for out-of-true. Anything more than 0.003" is a problem, and can be corrected with light taps of a small hammer. The dowel hole issue is harder to fix...
Another possibility:
The timing plate itself may be a little too small: we've seen this quite a bit lately on recent ignition parts. When setting this backing plate, try to lift it upward toward the top screw on the plate, and try to keep it "up there" while setting the 1-4 gap and timing. You may then find that the 2-3 gap comes in a little closer to spec.
Some of these backing plates (since about 2001) have been as much as 0.010" too small (of the ones I've measured) in diameter, making a lot of 'slop' and out-of-round timing errors.
