R wheels will probably rub on your fender liners, maybe other parts as well.t
My '96 855R had cut-away fender liners - about 50% of the liner was cut away to accommodate the Volan wheels.

Get the car on a lift to check clearances, including the rear of the exhaust system.

That '96 855R was a fine car - even the dealer's wife who formally owned it told me it was the best car she ever drove!

Did you know that 850's rear delta suspension steered the rear wheels in emergency turns.