John Deere 4052R Cab,, Deere 855D UTV, Z920A Zero Turn Mower and assorted implements
Your Kubota has 23 PTO HP...somewhat low for a 72" blower. But, now that you know your PTO HP, you can review the snowblower manfacturer's recommendation.
BTW, Welcome to TBN!!!
There are Kubota Buying and Operating forums, so you can see what other B3030 owners are using...
I've been running a 74" rear snow blower on a B7800 (22 PTO HP), which is the same chassis and engine as your B3030, for the past 7 winters with absolutely no power or weight problems. The secret is the HST. My only problem (and it's minor) is that I have to be very careful using the FEL with that wide blower on behind, so I don't sideswipe things.
Others will have more direct experience with your set up, but in general, whatever moves the snow to your satisfaction. Your engine is more powerful and modern than mine. I run close to wot but my engine is underpowered for my 60 inch blower. I go slow with the hst.
I doubt you'll have any trouble with yours at 2000 rpm.