John Clover was born abt. 1824 in Arkansas. In 1860 he and his family was living in Angelina Co. TX.
Supposedly he died 1869 in Bell Co., TX per Billington Family Tree but no documentation.
I also didn't find Susan Clover or Julia in a Census after 1860.
I'd contact the Bell County Texas genealogical and historical societies and ask if they have a local death index, indexed newspaper death notices and cemetery inventories.
Then I'd look for his probate records and Julia within those records.
George Massingill was born abt. 1823 in Arkansas. I'd look for his death and probate records and look for Susan's name. She won't appear in the 1840 Census because only head of household in any Census prior to 1850.
Look in FamilySearch, Location and local genealogical and historical societies for bible and baptismal records. Successful Searching!