I fitted new parabolics to my 88 last year. They're ok but car sits down on RHS slightly due to transfer box weight etc., original leaf springs are handed to avoid this.
I think mine are Britpart, but not certain of that or who actually made them.
There were several spring makers /suppliers represented at the recent Classic car show at the NECC in November, but I don't have a note of them. I think the quality can vary considerably - it's quite a job, so worth making sure everything is as good as it can be. You also need new longer dampers for parabolics. Nigel