1969 dodge dart 7 1/4 rearend rim offset and size

im looking to get a new set of rims for my 1969 dodge dart and im not sure of the offset and size, i think its a 15x7 height and width but thats all i know. how can i measure offset or will it be on the rim somewhere? the pic is what i have and the way it sits i want to keep it that way i just need new rims and i will be selling all 4 of these soon but 1 of the 3 is bent so that one will be thrown in free.
thanks in advance guys

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