I’m happy to provide additional feedback, but I’m unfortunately unable to setup a zoom meeting to create a crosswalk. I noticed however your other forum post here and this made me think that you are trying to merge summary data from census with US microdata on the city level; is this correct?
If so, you’ll notice that the IPUMS USA variable CITY has its own coding scheme which is different from place FIPS codes used by Census for cities. However, we include both place FIPS & IPUMS CITY codes in the "PUMA Match Summary" files available in the CITY comparability section. Summary data uses the FIPS codes, so those files enable linkages. Note too that 1980 was the last year in which the city of residence was directly identified for households in US microdata. Since 1990, microdata provides only the public use microdata area (PUMA) in which a given household resided. PUMAs are sometimes coterminous with city boundaries, but they also frequently encompass multiple cities and occasionally straddle city boundaries. Therefore, for most cities, and even for some very large cities, it is impossible to identify the exact set of records in the microdata file that correspond to a given city. CITY infers the city of residence by assigning PUMAs to cities in which the majority of each PUMA’s population resided. A household therefore might not in fact have resided in its identified city. This protocol yields errors of omission (where a CITY code is not assigned to some residents of the corresponding city) and errors of commission (where a CITY code is assigned to some non-residents). To ensure that CITY codes are generally representative of city populations, cities are identified only where the sum of match errors is less than 10% (see the comparability tab for the PUMA CITY match summary).
I hope this information helps you figure out how to best proceed.