Is it a Cub or alternative brand? Cub makes a 54", but it's designed for the 6000 series compacts. The Cub 48" was designed for the 5000 series compacts. I've got the Cub 45" blower (model 353) for my GT3200, (also used on my 3235 when I owned one) and it's a monster blower. It's actually the old 551 blower Cub used on the super garden tractors, which were a little bigger frame than the 3000 series.
I personally wouldn't go bigger than the 45", but I also don't know your application....assuming you have a long/wide driveway and a lot of snow to blow? If looking at the alternates, perhaps match up the weights of blowers so you know you're in the ball park....
good luck!