Gear Cables wont fit?

I bought some nice Simplex downtube shifters for my colnago build but the holes in them seem too small to slot the gear cable into! the cable goes through but the metal stopper thing on the end of the cable is too big! did the stopper used to be smaller? (the shifters are 80s) Would it be a safe/viable option to carefully file down the stoppers on the cable in order for it to fit? Once ive overcome this problem I actually need to install the cables and set up the mechs.. this should be interesting..
Thanks many.

Campag and shimano have different sized cable ends. Perhaps this is the problem.

Just UTFS and found this as I have the same problem... anyone know what the deal is?

Campag and shimano have different sized cable ends. Perhaps this is the problem.

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The ends are also of different shape. Perhaps try different inners?

Hmmm... I know its a real school boy question but it just seems daft... the cables without ends are still a little bit too big... and then I find it hard to believe the cables sit on bare metal runs under the BB?

GYAC - ditch the gears...

You have bought gear cables and not brake cables I trust. IIRC 1.2MM OD as opposed to 1.5MM OD for brake cables!!!

I don't know what GYAC means... but yeah....
Different OD's? I checked the cables I have and they are the same, a friend on mine who works in a bike shop sent them to me and it looks like he may of got it wrong...