Sysnode,
Both Sancti and Kilsyth have given you excellent advice.
In the 1881 census for 8 McAlpine Street Wishaw, Ellen F. Ferguson is the head of the house, she has supplied the information that her marital status is "married" (not a widow). All of the 7 children living at that address are her sons and daughters, all with the surname Gold. She supplied this information and, if she was unable to write, as seems to be the case, perhaps a neighbour or friend, or even one of the older children, filled the census form in on her behalf.
So the 2 youngest children were given the wrong surname.
Kilsyth very kindly gave you the birth information for Margaret, this would have cost him money, he has tried his very best to help. The information tells you that she was born as Ferguson.
He also gave you the information that the George born to Helen Frame/Gold/Ferguson was illegitimate. It would make perfect sense to revert back to the name Gold for the last 2 children and it would help her respectability once she went overseas.
Now, you say you have George's date of birth from his attestation papers for WWI. The year is ok but the day and month wrong. Well, don't forget his mother would not be able to tell him the correct date and it is a very common occurance in family trees, my own included. I had a great aunt who died in 1974, she swore blind her birthday was 1st May 1888. After she died I sent to Ireland for her birth certificate, she was 2 months younger than she thought!
Cambusnethan parish was very small, about 3 families by the name of Gold are recorded in the 1881 census. Only one fits the description of yours, without a doubt.
Now you can look further back at the next generation - supplied by Kilsyth - Daniel Gold and Grace Clarkson.
It may interest you to know that in the 1881 census, 2 pages on from McAlpine St, at Graham's Land, there was a Daniel Gold aged 73 years, a widower, born Douglas parish Lanarkshire, living as a boarder with a family named McAuslin.If you agree that Daniel and Grace were the parents of James I can perhaps, give you some other information.
Regards,
Lodger