It's possible to setup a relationship that matches values on all these fields.
LargeSigns::IRS = SmallSigns::IRS AND
LargeSigns::TAC = SmallSigns::TAC AND
LargeSigns::Street = SmallSigns Street AND
//continue this pattern with the othere fields AND
LargeSigns::Group Number_Manager = SmallSigns::Group Number_Manager
You can then write a script that steps through either the records in the LargeSigns or SmallSigns table and stops to use some Set FIeld steps to merge the data whenever a matching related record exists.
When testing such a script, make a back up copy of your file first, so that you can throw out your file and start over if you get data merged incorrectly.
It took a lot of back and forth editing on the initial addresses to match the similar addresses.
What I did was write one script to refresh the imported data, then another to merge them. Once happy with the performance I just combined them into one script that would wipe out all records from each table and re-import them from a clean copy in another file.
Then I ran into the discovery that related records don't relate when matching fields are blank. Added more script steps to insert a text placeholder to allow the match, then remove it later.
I'd then do a search (manually) for duplicate or similar addresses and manually correct them. Royal pain but I couldn't think of any other way than manually editing the original lists I was provided. In the end though I got thanks to your suggestions PMJ.
I just did some quick weight calculations in excel that I could have easily done in FM also and sorted my packages by weight with a report and export to .csv files for importing into UPS Worldship (another nightmare).