Having both B3030 and L4740 tractors and similar blower setup, there is no way this subframe would work on a B series tractor. It is way too long and the weight of the L's series blower is substantially more than the B size blowers.
Look for implements that start with a B or even BX to fit your tractor, not L as in L2180.
Good luck in your quest for a front snowblower.