You will need the 32mm manifold too, or make an adaptor plate and bore out the hole to 32mm if you feel skilled enough. Depending of what version of the 28mm manifold you have, it may or may not have smaller ports compared to the 32mm manifold.
If the 32IF was not from an 845 engine, you will also need the suitable jets.
Also the 32mm carburettor base was water-heated, the original setup had a special head with a water take-off, and another T-junction at the bottom heater hose. I think water heating should be necessary for your cold climate, so your best solution would be to use two T-junctions on the heater hoses.
Renault used to combine the larger carburettor with a different distributor having a vacuum advance unit. Centrifugal advance curve is the same (R284) as on other 845s. The ideal solution would be to find that distributor, too.
I have driven a couple of R4s equipped with this setup, and it makes a noticeable difference, especially in bottom to middle torque, and engine smoothness.