Basically, you have to change the condenser and the negative mask. Maybe a longer lens as well, but that will depend on the lens that you already have.
It will depend also on the enalrger series from Kaiser, but for series 5 and 6 these are teh Kaiser references: the condenser is Ref. 4449 (up to 6x9) and the 6x7 mask is 4436. I did this change some years ago and had a problem with the masks, so I decided no to use masks but a couple of antinewton glasses (4487).