I get the feeling that the left BB cup is sticking out too much - not the spindle - because the OP says he put a 73mm spindle in a Super Course. A Super Course would have a 71mm bottom bracket.
The 73mm conversion only works on the Raleigh Twenty. If I have interpreted this right, the OP needs to find a 71mm 5-series spindle, or a suitable 70mm Italian spindle.
-Kurt
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