A couple of years ago maybe 2009/2010 they stopped making the older style curtain glide tape. That tape had the pieces that slide into the track. They now only seem to manufacture a glide tape where the track slides into the glides on the tape. It is suppose to be more durable.
There are places that sell items that you can sew onto your curtains that will glide in the old style track. I have experimented with several and had good results.
If your curtains are not falling apart from dry rot...you can wash them and then dye them ...I did with good results. Do not dry them in the dryer they will SHRINK.
Hang them back up damp and let them air dry.
This works well just whip stitch it on...sort of like a button with a shank.
http://www.vintagetrailersupply.com/..._p/vts-475.htm
This works well and you can sew it on by hand or machine:
http://www.vintagetrailersupply.com/..._p/vts-354.htm
I have not tried this...but this is what you would use with the snap tape...sew the snap tape on ...snap these one and slide through the track.
http://www.vintagetrailersupply.com/..._p/vts-553.htm
This is the snap tape:
http://www.vintagetrailersupply.com/..._p/vts-551.htm
Every once in a while someone will say that they found some of the old style tape...but trust me..I have googled to the ends of the earth and cannot find it.
After I retire I will play around with making a Roman shade that won't stick out too far. All the ready made one that I have found stick out to far.