B20 is the backhoe variant of the B1750. Are you looking to replace the backhoe on it with a Woods model? Your best bet to get the proper subframe would be to contact woods. Sounds like the BH70-X is the right size for that model and subframes usually mount different models like the BH70 or BH80 and may still work with the BH65.
Unless the spacing on the tractor is the same as the subframe, I don't think it will direct adapt to a Woods.
