Good looking tractor, congrats.
I'd like a 216 also, but havent found 1, yet.
As for the seat springs being reversed.
It probably moved the seat back for legroom, or to fit that seat. The seat is a replacement. So try it either way, what fits you is best.
The mower deck looks to be a newer model also. Your 216 would have had a 38in or 46in deck. The 46in deck is a model 47 deck, and look like this...
Try and get belt numbers for the blades and the PTO drive. Since that deck didnt come with it, the stock parts lookup won't help. If you cant find any numbers on the belts, remove them and get them measured and matched up. And I recommend JD belts only. They fit and last.
You have a great tractor that with proper maintenance will outlast us all.
Ohh, and get your wife to smile when on the 216.
I cant stop smiling when I'm on my old 212.