Which BIRCH is correct for my purpose?

Honesty to get it uniform you will need to replace all of it or at least sand down the original stuff and re-shellac it, otherwise it will not look the same due to the natural yellowing that has taken place over the last 50 years.

So that is good to know! Is bendable 1/8" birch what I need to purchase?

Wait just a minute here now... LOL... This isn't my first try with shellac matching by any sense of the word. It's just the first time I have done it before installation of the panels. Normally I have it running down my arm for 5 coats but still get a fantastic match. I really like doing it your way though. This isn't the french polish. It's done with a really good and expensive brush. But I'm pre-finishing all the new paneling before it get's installed and I like a few things about it.

1. No shellac running down your arm. I'm doing all five coats before installation.
2. I'm not getting amber shellac on the welting/gimp... That's a huge plus.
3. I'm not stuck in a small area with all the fumes. Big plus.

So thanks for the great advice John. It's really much better doing it this way. I do want to try the french polish but on a trailer that is not in any hurry to get done. This one has been waiting 6 months for my eye to heal so I need to get after it and get it done. And thanks for the good critique.

No Ann. 3 coats of Amber colored shellac gives it the depth of color needed to match what is there. 2 coats is a little lighter, 4 coats would be darker. The more coats of Amber Shellac you do, the darker the color. Then once I have the color right, I begin adding coats of clear shellac... Two will do this trailer just fine but I have gone as far as 3 coats of clear before.

Yes this is very time consuming. I figure I have at least 4 to 5 hours not including drying time into each sheet of paneling. And that doesn't include planning time or clean up at the end of the day. When all is said and done if I sell a trailer I figure if I'm lucky I may make a few thousand dollars which translates into a few bucks an hour. Some trailers I lost money on and others I broke even on. I made $1.78 on my Lil Loafer. 

We make fun of flippers, but they make the real money. No worrying about replacement birch or shellac, just buy it for $500, clean it, sell it for $2000 on eBay.

Some of you sharpshooters have such a following you'll sell a restored canned ham for $15,000 to $20,000. But for most of us selling on CL, $8,000-$10,000 is top dollar. So $1.78 an hour sounds sweet to me!