I have a Sekai 2400 frame/fork from 1983 that I want to raise from the dead. The bike was made for a 6-speed freewheel, 27-inch wheels and nutted sidepull brakes. I have the original wheels and would like to add some components from that era to complete the build. I'd like to use indexed downtube shifters. Did they make indexed shifters for 6-speeds back then? What model brakes and shifters would fit my needs? Although I could buy all new components from Harris, I think it'd be fun, and cheaper, to find used stuff. Thanks.