I got some nice tires and wheels made by Le Mans Miniatures for slot cars; in my case, I got excellent piano wire wheels for the very good 1/32 Bugatti T59 kits by Pyro and AMT. This source has a few, but look around at various slot car parts suppliers: http://www.ncphobbies.com/slot-cars-1/32/
Also available in a Monogram metal body version. Just keep checking eBay from time to time and you may find an acceptable price with shipping. I don't know if it's the same as the Testors / Bburago metal body kit.
I've seen plenty of leather, fabric and other material gun cases for a single, fully assembled shotgun, but not like the one you're making. But I guess It would be custom-made anyway. This project looks fabulous.
You'll notice in the link to a built kit (one of the best I've seen) that the hood doesn't fit properly and needs attention. Again, you'll want to find some larger tires. As mentioned, lots of detailing and accurizing needed. The windshield frame needs attention, too. The Lindbergh box is very misleading since it shows a 1:1 car, but at least it provides reference.