Hello Barbara,
A man who had a lot of information for me was, Allan Kelly, Tel: 01624 843897
Fax: 01624 844219 E-Mail: manncol@advsys.co.uk. He is a Manx historian.
Also, the Manx Museum has copies of Wills,
which they will print out for you at 10 or 15 p.
per sheet.
If your g-grandfather was 70 in 1920 he would be born 1850. If you let me know more details,
I will look at the IOM census for 1851, and let you have any details I find -ok? On average, the chances that he lived no longer than say 76, would mean that you are looking for published Wills 1926-1930. Let me know you need any more help.
Regards John