Nice find. A few things about pan cars...
One, those axles have been used successfully for 30+ years. The 1/8th shafts are not a strength concern, but threads on them are nice for using 4-40 screws instead of C-clips. Actually, aluminum axles are less durable than the smaller steel ones. You can find the threaded axles from any contemporary 1/12th scale manufacturer like CRC or SpeedMerchant. What you have is perfect, and I wouldn't have changed them.
Next, that front end on the 10L is affectionately called the "old school" front end by racers today. It's primitive, but it works. The problem with your brace is that it's not necessary, and it will interfere with the steering and any ability to change caster and camber on that front end. It's done with shims, and right now, you have none. It will be hellacious to drive that way. Zero caster on an oval car is a handful, to say the least. I would ditch the brace, or at least revise it to not tie it into the antenna mount. Tie the front together, it will increase lateral stiffness, but elongate the holes to allow camber adjustments under the suspension blocks. I'm about 99% sure that front end brace will interfere with the steering linkage anyway. There is a lot of layover of the links when the steering is at full lock.
To true tires... in on road or racing with foam tires, a truer is essential to making the car handle and stay consistent. And in controlling the proper ride height. Find a local carpet track or carpet racer—chances are they will have a truer with on-road arbors that can true your tires to the proper sizes and shapes. Even if you aren't planning on racing it, it looks 1000 times better than a hack job here. Most race tires don't have a whole lot of foam on them for ride height, and to reduce foam squirm in the corners. Lighter is better.
The LTO chassis is Left Turn Only. It's an oval chassis and won't turn right very well with all of the weight bias. Your other chassis is also an oval chassis, but will allow you to balance everything down the middle for using on a road course.
Hope this helps...
dc