I don't know who you're buying from, but if Mendelsohn I'd phone them up for a chat. They convinced me, when I was installing a G5 and GNC255, that I could do it myself.
I've not used a KRT2. There is a suggestion that they don't come with connection kit at all. Their manual seems to recommend either a small circuit board (ST1 p46) or some other adapter (STX) rather than wiring straight, which suggests they have had problems with DIYers. I see there are adapters available from some suppliers to convert wiring from various makes into a KRT-2
https://lxavionics.co.uk/index.php?rout ... uct_id=699 I suspect that soldering in an aircraft isn't easy. When I installed Garmin and Trig kit, all parts came with connections, and they were all crimp.