That sounds fun, love those old KG's. Maybe someday I'll do a swap like that into my '90 1.8T Corrado.
For the kart I'll be using a single battery. Currently that is composed of 420 Molicel P26A 18650 cells in a 42S10P configuration, so a little less than one of your modules of 444 cells. Peak amperage will be 350A. The cells alone are 19.4kg, but with the case, shielding, etc it will be a fair bit more. All in all, in karting the driver is about 1/2 the total weight. For the 100cc TAG class, the minimum weight is 175kg with the driver, so I'll be a bit on the heavy side. However that also includes front brakes for added safety, so that adds a little weight over the rear-brake only TAGs. It certainly will be much quieter than the old 2-stroke Honda motocross engine I was running.