John, one potential problem to look out for: The keypads for your 6112 (I think it's D636) support expansion zones taken off the keypad(s). If you have more than 8 zones in your system, you might want to check the wiring in your keypad(s) to see if their expansion zones are used. IIRC, each D636 KP can add up to 3 zones to the system. Hopefully you have a zone list somewhere to tell you what doors, windows, motion sensors, etc, are on which zones.
If you have keypad expansion zones, you'll want to be sure what provision your Concord keypads have to replace them. It's been years since I worked with a GE and I don't know what the current keypads support in the way of expansion zones....that's IF your Radionics keypads use them.
Also--when you get around to replacing the keypads, you may notice that your new keypads will be wired differently than your old KPs. The 6112 KP data loops were wired in series, while ALL other keypad data loops that I'm aware of are wired in parallel.
(That was extremely annoying when I had to work on a 6112 system with a bad keypad: One bad keypad knocked out all the other keypads and you couldn't just disconnect it until the tech could get there. Taking a keypad out of the loop would cause the others to scream until it was replaced or the panel reprogrammed not to look for it.)
And BTW, I'm one of those techs who will argue with Mike about the need to place EOLRs out at the last contact in a zone loop. That's because I spend decades troubleshooting problems in systems. One of the trickiest problems to find is the source of an intermittent false alarm. One of my first things to check is the zone loop resistance, which CANNOT BE READ WITH THE RESISTOR IN THE LOOP. And I want to read the loop resistance BEFORE I fiddle with any contacts: Jiggling a contact can make a flaky contact resistance temporarily disappear. If I have to remove a contact from its setting to access the resistor to bypass it, then I can't be sure I haven't affected the loop resistance before reading it. When the resistor is in the panel, I can read loop resistance before examining or jiggling any individual contacts.
Unfortunately, I do have to agree that EOLRs in a commercial/institutional system do need to be placed at the last sensor in the loop, to prevent circumvention by employees and/or public; but that's usually not a concern in a private home.