Please read your welcome message before posting again. "1957" subject does not summarize your post. Also, as your welcome message says, cars for sale or the discussion of buying and selling cars goes in the cars for sale forum which your post is being moved to now.
In a way it does but in another way it doesn't. It all depends on any prospective buyer. If it's some one who want s the benefit of a later engine then it'd more valuable to him then a car with an original (old) engine
@Jerry m , it depends on what you want. If you want a car that you can drive a lot the 302 is a very good choice. As to the value, it's worth what you are willing to pay.
Are you looking for long term ownership or short term/ flip?
Of course it does. The reason is simple. It limits the market of buyers, some people won't have anything to do with a car like that. Unless it's a full restomod, personally I would avoid it all together and keep looking.
If it doesn't bother you, go for it as long as you are not paying for price of an original. If you want a fun car, the 302 will be fine. If you are determined to have a completely original bird, walk. Only you can determine if it is a good thing or not. To answer the original question, yes it does affect the value. Happy cruising.