Hi Chaps,
when I put the headlights on when my 360glt is at tickover the revs drop to about 400rpm and it nearly cuts out, obviously this can be rectified by adding throttle, but any ideas why this happens?
oh its been stood 10 years in a barn, so maybe some WD40 on the alternator?

Just take the belt off and see if the alternator is actually stiff. If not it's possible a bad connection is causing very high resistance.

Is the engine producing normal power, have you driven it? You should be able to let the clutch out slowly on tick over, especially if its high compression (1986 or less).