How it is possible to make a candala a Vaisnava?" No, that is possible. Prabhavisnave namah. Visnu is so powerful, omnipotent. He can do that. So only by Visnu mantra, by becoming a Vaisnava, one can transcend all this restriction, sociology
-Lecture on Bhagavad-Gita 1.40 -- London, July 28, 1973

श्रोत्रं चक्षु: स्पर्शनं च रसनं घ्राणमेव च ।
अधिष्ठाय मनश्चायं विषयानुपसेवते ॥ ९ ॥
The living entity, thus taking another gross body, obtains a certain type of ear, eye, tongue, nose and sense of touch, which are grouped about the mind. He thus enjoys a particular set of sense objects.
-Bhagavad-Gita Chapter 15 Verse 9