If you have not already done so, go over to the American Single Shot Rifle Association website (ASSRA.com) and look around. Ask for me (same screen name, Green Frog) or send me a PM here if you need help finding something. In addition, I've also seen both of the parts you need on eBay quite recently. They weren't all that expensive. There is a vendor named drwinchester as well as others who offer such parts often.
As others have said, you will need to know whether you are seeking a leaf spring (earlier) of coil spring (later) action. The hammer requires it and the block only interchanges one way.
If all of this is sounding like Greek to you, just go over and hang out on the ASSRA forum, then sign in and under the Gunsmithing forum repeat your question you posed here and some real experts will chime in! BTW, low walls make great 32 S&W Long or 32 H&R rifles, I've had 2 of them.
Forggie
PS. I'm currently building a low wall I bought as a stripped action. It will be a 25-20 SS when done. Also, if all you can find is a rimfire breech block, they are easily bushed to CF. If it is a 22 block, that's all you need to do. other RF blocks (32 RF are the most common) may require a little more fiddling, but it cn be done.