I agree that those on the old scheme should be on the same rate as the new.
The link in my last post confirms what I thought however, which is that under the old scheme women had to pay in for 30 years, not 39.
I doubt that most women paid anything like 30 years' of contributions, though - many didn't work whilst their children were at school, and back then their 'contributions' were paid by the state until the youngest child was 16, so with a large family that could easily be 25 years. When the new scheme came in, this was cut to when the youngest is 12, which added to the number of years that needed to be paid, along with the increase to 35 years.
Nevertheless, we all live with the same living costs, so there is no reason why older people should receive less - it's not like they get discounts on food or rent.