5 x 4 1/2 pattern on 67 barracuda

Looking for information on why a 67 318
Car would have the big bolt pattern?
So I'm getting ready to do a disc brake conversion on a 67 cuda and it has the big bolt pattern drums on the front. Are these things worth saving? Do I still change the upper a arm? Why the big pattern, and the big question who makes the best conversion without junk Chinese parts?, if there is one. LOL