Tire advice

[SuperChief]

I am trying to convince a young man who has an 83 shortbed to not change the wheels to aftermarket with newer bolt pattern. I would like him to keep the truk stock. He thinks replacement tires are too expensive and wants to change.. I did research and his door panel states size of 275/60/R15 I think a replacement tire of 235/75 R15 is in his price range to keep the stock rims. Are there any pitfalls in recommending this to him? I am sorry if this doesn't belong here but I am 75 and he is in his 20s and this was his Dad's truck. any advice would be appreciated.