reverse light...socket delima!

well here is the situation my dad and i got a 73 dart swinger so that we could have a project car to fix up and I am new to the forum. I was wanting to know how i would go about replacing the rear reverse light socket. When we got it, it was rusted out and was a pain to get out and we have tried various socket fittings and we have had no luck, we very well might be replacing it wrong so we need some help.
thanks