AMP360 or Jim from the Fret Shop in Vernon can probably help you.
Basically it sounds like you have a true vintage spec 54. Which means the neck pickup is actually setup to play bass. Back in the old days folks actually played bass on a tele. The middle position on the selector is actually the rhythm pickup and third position is bridge.
Basically I think all you need to do is change out the cap --- but you might also want to wire it differently so position one is neck position 2 is neck and bridge and position 3 is bridge.
Jim (he posts here) owns the Fret shop FRET SHOP in Vernon. He does great work (fast!). He has done all the work on my guitars for the past 7-8 years.