will 3 1/2" offsets fit? Alum slots on 74 Duster?

I have a chance to buy Two 14"x7" with 3 1/2" back space and two 14"x9" with 3 1/2" back space. All four wheels are old school, car five lug, uni-lug, fit Chevy, Ford, Mopar, AMC. The guy wants $325 for the set and are Fentons. Said they have never seen salt/ winter. They also have the center caps. They look exactly like what was on my car when I sold them almost 20 years ago. I am just not sure if they are the right offset for my 74 Duster. Is this a good price? I have seen used alum slots for 200 but usually not with centers and polished and no winter use on them. What do you all think? I have 2 full sets of 14' Ralleyes but I want to get the wider tires for the back. The 14x7's wont get tire rub on the fenders will they?