I'm partial to the Cat Comfort Seats. Lots of options and in the same price range of the aftermarket ones. Especially if you factor in shipping vs a local dealer stock order. You can buy parts for them and the cushions are easy to source and replace.
There are real liability concern with seats and seat belts and cab certification. The ROPS, seat and belt are designed to secure an operator in place during a rollover. If you change any of that, now you own it.
Of course, that's not probably a concern if this 980B never leaves the farm.