I haven't fitted them myself, but had a 127 with rear 3 point static belts fitted by the previous owner. There are plenty of 3 point static belts advertised for 127's (Ebay, or perhaps more reputable:
I don't know if the mounting points are there - I'd guess yes as they were very neat in the 127 I had.
Maybe someone else can confirm?
On a slightly different note, how about Santa Pod, or Shelsley Walsh hillclimb retro events this year? I'm in the process of applying & will post the events up soon.
I think I remember when I first put the car back on the road there was a threaded bolt in the back wheel arch,just not sure where the other two points would attatch.The static belts on ebay are the ones I was looking at.
Probably do Santa Pod this year after not going last year,also Retro Rides at Shelsey Walsh,that's about as far as I'd planned.Be nice to find some events I've not been to before.