Hi and welcome!
Why do sellers claim a set "works" if, when they plug it in, that some of the tubes light up but nothing else happens?
Well, here's the inside scoop on your set. It is a very nice radio and capable of great sound. That's the "pro" of the 41-300. The con: Rubber-covered wiring. Like all Philcos made between 1939 and 1942, your 41-300 is full of wires insulated with rubber. The rubber has a bad habit of drying out and flaking off the wires, which can create a safety hazard. These must be replaced for safety and reliability.
There are three ways to do this:
1. Remove the insulation from each wire, one at a time, by unsoldering one end and then adding the proper length of color-coded heat shrink tubing over the bare wire. Then resolder and move on to the next wire. This will have to be done to every rubber insulated wire in the radio. I don't care of the rubber is still soft and pliable. Check it again in 20 years and get back to me; if it isn't hardened yet, it surely will be sooner or later.
2. Unsolder one end of each wire and put color-coded heat shrink tubing over the old wire, including the old, brittle insulation; then resoldering that end and moving on to the next wire.
3. Replace each wire in the set with new, plastic coated wire of the proper size and color.
I used to think that it was a bit easier to use method 1 above, but after redoing a couple Philcos recently with rubber-covered wires and trying method 3, I think I like that method better. I do not recommend method 2. In my opinion, if the job is worth doing at all, it is worth doing right.
Now to answer your questions in order:
What is a the best source of tubes?
My opinion: Bob Dobush -
http://www.findatube.com/
Keep in mind, though, that tubes in an old radio are often still good. They should not be replaced unless they are known to be bad.
Is there an index that matches Philco radios to the type of grille clothes?
Nope. There is no grille cloth available at this time. Radio Daze and Kenny Richmond are both working on bringing back some of the patterns that were available as reproductions, but I think the 41-300 used something very plain and generic as you can't really see the cloth in that model anyway?
I had an idea of trying to put together an index of which reproduction cloth matched what Philco models, and then the person who formerly supplied reproduction cloth retired because the company that was making the cloth for him quit making it. So, that put an end to that idea.
It could stand to be refinished. Does anyone have a resource of brochures or other info that could describe how the original was done?
Here, I will defer to others more skilled in cabinet refinishing than I. I will ask, however: Are you sure it needs to be refinished, or does it just have some minor scratches/scuffing? That can be corrected, to a certain extent, without refinishing.
There are holes directly above the pushbuttons for the call signs. I haven't seen a clear enough picture to understand what is missing.
Just look here:
http://www.philcoradio.com/phorum/showth...p?tid=4355