As others have said, proceed with great caution.
It may not be possible or practical to use that frame.
If you can use the frame safely it will be really easy to waste a lot of money buying parts for it that aren't compatible.
The six speed rear cluster is either Uniglide cassette or freewheel. Most indexed shifters on the market will not be compatible. It would be simpler, less expensive, and more trouble free to use the old shifters or similar shifters.