I want to study the Californian gold rush, the movement of ppl into califormnia, the winners and loosers (based on their property values in the decades after). The gold rush took place in ~1849-1855, I cna obviously use the 1850 and 1860 full counts but that would likely encompass loads of post gold-rush migration into california. In 1852 California did a state census, I know familysearch.org has scans, as do others. If I can find, or create, a digitized dataset (or talk to people who have it), would there be a procedure that lets me link it to the IPUMs full count datasets? I could fuzzy match on age,sex place/quarter of birth etc, but ideally id obviously match on name.
Both the 1850 and 1860 full count federal census microdata on IPUMS USA include the variable BPL (birthplace) for all persons. Additionally, the IPUMS Multigenerational Longitudinal Panel (MLP) provides de-identified census microdata that links persons between their appearances across years in the full count census. By requesting a linked 1850-1860 file, you would be able to identify people who moved to California between the two decennial censuses. However, as you note, it would not allow you to separately identify those who moved in from 1851-1855 from those who moved in after the rush in 1856-1860.
IPUMS USA does not have data from the 1852 California Census. If you were to obtain this data, you would certainly want to match persons to the 1850 full count data by name. Note that through the North Atlantic Population Project (NAPP), IPUMS-International provides microdata that includes the first (NAMEFRST) and last (NAMELAST) names of all persons in the 1850 federal census that you might use for this project. Alternativity, you may apply for a restricted use license to access this identifying information on IPUMS USA.