Welcome

Thanks!

Corrected all that needed it (most are ex-USPS trucks, which were Chevy trucks.)

OK I renamed them using the info in comments when they seemed reliable.
So a few are unknown, if you have time to check these...
Here are all those previously listed as UCBC make, now they have it as extra info:
http://imcdb.org/vehicles.php?resultsStyle=asImages&yearFrom=&yearTo=&makeMatch=- 2&make=&modelMatch=1&model=UCBC&modelInclExtra=on&origin=&madein=&madefor=&role=

Rename them to the original make and model that they had (I can help on some of the unknowns). For the others, just make them unknown where no make was given if nobody can find one.

ok but then what should we do with these?
Rename to the name suggested in comment (like Grumman for the one in the 2nd link)?
And unknown for those where no other make was given?

"rmeneses" is incorrect about calling all of these vans "UCBC" vans: http://imcdb.org/vehicles.php?make=UCBC&model=&modelMatch=2&modelInclChassis=on
While the Union City Body Company did make those bodies, the designations like Chevrolet Step Van and Grumman Step Van are correct. If anything, you can put "Union City Body Company" as additional info. Read more here: http://imcdb.org/vehicle_123337-UCBC.html