never heard of a '79 with kck only, has it wire wheels and drum brakes?
if you want to have electric start ( got rid of mine for the tracker and it lost 10 lbs in weight) there should be a silver cover on top of the engine under the carbs. have a squidge in there and see if there are the mount holes (2) to fit one. failing that, buy a duff xs250 engine and you can use the bottom end of that and put on the 400 barrells and carbs!
don;t forget you will need to wire in the solinoid and switch etc.
head over to www.xs400.com its about xs400's ya know!