1969 C10 Side Mirrors

[mbright]

I'm sure this is an easy question. On my 1969 C10 I ordered reproduction mirrors from LMC. The reproduction mirrors have three holes, but the ones on my doors only have two.

I would rather have the reproduction mirrors because they are bigger. LMC said these mirrors should fit all models. Is it as simple as drilling the third and final hole in the door and screwing it in?

I will post pictures when I get home if I'm not making myself clear.