Python or Ssnake Oyl will make a set. Buy any correct buckles (think they sell them too, but restoring a good used set is cheaper) but 50 year old webbing may be suspect, but "can" be redyed if safety is not a big concern.
Some interesting info on old seat belts. I just read it the other day and it made me glad I replaced the webbing on my belts in all the cars when I restored them. And that they are garaged and covered. Some scary info/numbers in there on the performance of older belts (and only a decade or so, not 40+ years)...
Just one view, but have seen similar issues elsewhere. Food for thought...
http://www.dogandlemon.com/articles/tragic-lack-restraint
A few quick excerpts that caught my attention, for those that may not want to read the whole thing;
Further, any belt over ten years old is possibly seriously weakened by sun damage.
As a convertible owner, kinda relevant on that one for sure!
Excessive stretching – all seatbelts stretch a little bit. If they didn’t they would probably cut you in half during a serious accident. ... We are sorry to say that many seatbelts of this type over five years old – and some current models – are highly suspect.
It is estimated that a 5mm cut in the belt’s webbing can reduce its effectiveness by half.
That's about 3/16", a "tiny" cut/tear.
Not being alarmist, as with most of these old cars its well documented the owners are some of the safest drivers around (why risk your pride and joy or damage to the recent resto, its hard work!!) but the article just raised my awareness of the risk of sticking to original (as I, and many here, like to do) in this area.
A small compromise that I can live with, and am glad I did...
