I saw a PILE of old beater C100's at an auction last weekend. No way I was going to even touch those old things. There are way too many nice ones out there for near nothing just like the one you found. That thing is cherry.
And the K bike! I've ridden a few of those. I almost considered buying one when I was young but the heavy hitting inline 4's were just too exciting. I've always wanted one but I'll leave all the fun to you. That's a super nice bike but yes it does need some zing. It's do-able though. I can't wait to see what you come up with.
Very cool.