I think your biggest problem will be with the ladder- that cabinets wired for a certain machine with certain functions...simple things like cycle start or hold will require fooling inputs that the t/c is retracted, stuff like that, plus what if their logic requires homing all 3 axes before cycle start...you can dummy out the third axis with 2 simple plugs, but you'll likely need to get into the logic to be able to run it.
your best bet will be to get a copy of the old IBM fladder, edit your existing ladder in ram to suit your needs...if youve got anyone that does any brand of plc work, they should be able to sort it out easily- Fanucs PMCs are one of the simplest to work with out there...you would need a pcwriter eprom burner too to read in the old ladder, and burn your final copy once finished...come to think of it- theres a ladder editor card you can plug in to a -C control (should work on a mate) Ive never used it, but think it might work too...but editing ladder without text sucks- maybe the editor adds text, but I doubt it. I dont know if the editor has eprom sockets, or if it requires pcwriter to upload eproms.
if you can find a local retrofitter, he could probably get you 90% ready to start wiring in a hour or two, maybe another couple hours fine tuning functions... theres a company in Canada that makes great cables very reasonable (we get their robot pendant cables- they take a lot of abuse and we never seem to have time to make them up) one thing about fanuc cables though- you might need to go huge on sealtite, or split flange your cable inlets if you buy premade...think you need a 1" knockout or bigger to fit a honda plug thru- even with the shell removed...the cables are not difficult to make at all, you can usually find the honda and amphenol plugs on ebay for cheap- if you do make your own just be certain to triplecheck you put all the amphenol shell pieces on before you start soldering- Ive pissed myself off soooo many times getting distracted and forgetting a clamp or something
*If you buy honda plugs, get the solder type- crimpers for the crimp type plugs are very hard to come by...I actually found a pair on ebay for 15 bucks-made my day, as honda charges like 700 bucks for a pair!!! they work great, make perfect plugs, but are about rare as hens teeth to find reasonably priced...other crimpers like the little radio shack rs232 pin crimpers *can* work in a pinch, but you'll need to solder them after crimping to be sure they hold...good luck
Tim