what you need to do a five lug conversion on a 65-66 mustang is a set of 65-66 V8 spindles, or a set of 67-79 spindles. at this point it is just as easy to convert to disc brakes as it is to stay with drum brakes. you will also need the change the outer tie rod ends as the V8 ones are larger the six cylinder ones. the 67 drag link is too long to use in the 66 car, and the
control arms are enough different that they also cannot be used.