Putting the powerflow from the 62C onto the 54C deck was a non-issue. It fit just fine without any modifications and works great.
Edit: Add pics and more description.
I have attached a couple pics of the powerflow installation, coupled with my 20 cu ft wood collection box, built over 20 years ago. There's not much more to say about mounting the powerflow to the 54C. It just went right on, and works. It's actually easier to mount/dismount when I think back to the smaller power flow I had on the 332 with the 48" replacement deck.
This collection box was used regularly on my 318, then on the 332, using the mounting bracket I took off the hydraulic tiller. Now the mounting was adapted to 3 PT with the 2210. I had JD's big collection system on the 318 way back, and hated it because it was miserable to mount/dismount from the tractor. I need attachments that can go on and off the machine in minutes with little effort. I'm not a fan of "baggers" because of the heavy weight of having to lift these bags to dump, especially if working with wet/damp grass clippings. So I chose to build this large capacity box, which has served beyond expectations. It's light, easy to mount, and holds a tremendous amount of stuff, greatly reducing the time spent going back and forth to the compost pile. The only downside to it is that material needs to raked out onto the ground. I've considered designing a new collection box that has an auto-dump feature, but that hasn't happened yet, and this has worked fine for many years.