I am pretty sure I have answered this for myself, but I thought I would double check here. I have missing thimbles to replace on a mid 19th century half stock. It looks like tin-lead solder was used originally. I assume I should use the same to attach the replacement thimbles. However, I had wondered about using the 430F tin-silver solder. I have a jewelers torch and can be pretty precise in my heat application. I should also note that the rib is quite firmly attached and I don't want to have to re-solder it. Let me know what you think.
I am just doing some light conservation work to this rifle. It just needs a cleaning and the two forward thimbles. It has a poured pewter ramrod entry.