There is an article about using the HW-101 and SB-102 on the AM Window here:
http://www.amwindow.org/tech/htm/hw100plusmods.htmI have done this mod with the HW-100, and it works well.
The architecture of the HW and SB rigs here is so similar, I would be very surprised if this mod did not work for you.
If you follow just the three steps in the first paragraph, you will be on the air, no mods that are not easily reversible. The other mods give you audio improvements.
Your 301/401 pair look very nice. I would crank up the 401; it probably does not need any major TLC....
Give it a try, let us know how it works for you. You will probably find it makes a great driver for a linear amplifier as well.