From copnversations I had with Bob Crump, his voicing of the JC-1 was specifically around the Nichicon caps. In fact you should also see some bypass caps at the end of the rails. These used to be Relcap RT's and Nichicon KZ's, I believe.
Chanking out the cap brands will most definitely affect the voicing of the amp.
Chanking out the cap brands will most definitely affect the voicing of the amp.