I'd want to know a little more what the FORD dealer planned on changing. Generally you need to at least change the Accumulator, and add a high side overpressure cutout switch, and change the expansion valve. Someone said FORD had started adding larger condensors, but I doubt the truth of that, esp. in your case for $600. (a larger condensor, should a retro be available would be a GREAT idea, btw). $600 sounds high to me, but I don't know what components they might be changing other than what I said above.
They will need to evacuate and flush the system, add the new components and they might be considering adding barrier hoses - although there is a mixed verdict on the necessity of that if they have been running with an R-12 mineral oil lubricated system as mineral oil apparently gives a similar "barrier", add ester oil (or possibly PAG), and then draw a good vacuum and add refrigerant.
The dealer will probably get $75 for the accumulator, $50-$75 for other parts and $40 for the refrigerant. There may be a recovery and disposal fee, and probably 3 hours labor.
That's about the best I can do. Let us know how it all works out. I recommend against cutting corners on a conversion... Penny wise and pound foolish.
Cool exploring
Chris
ps. there is a thread in useful threads on converting to 134 which might help a little.
