Brake upgrade on a 65 cuda

Yes, but... That particular kit is advertised as B body discs. B body rotors are 11.75" not 11". A body discs are 10.87" There are some great articles on the conversion, one of the earliest and best is "Disc-O-Tech" by Richard Ehrenberg. I highly recommend you read this before spending a penny on anything. There are many sources for kits now available using all new parts vs having to find and recondition used factory parts like we did years ago. All depends on your budget and mechanical abilities.