Personally, I've found the early rewinds as used in the 1966 R&C series hard to find today. Mura, Lenz and French arms and motors are listed in the 1966 1/2 Auto World Catalog. Maybe they are just all used up.......or blown up. 
I've mostly used a hybrid Mabuchi motor I call the 66/68 Hybrid Mabuchi for my R&C builds. Basically it's a 1968 Mabuchi motor with the armature (I like the red wire version) epoxied and static balanced to look like an early rewind and the can replaced with the earlier blind bearing or gimbal bearing version.
This hybrid motor is usually 65 turns of 30 wire with an ohm reading of .8 which duplicates the milder winds in the series pretty well. They run cool, have brakes and are great fun.
The 68 Mabuchi motors turn up on eBay and are often found in little Wamp cars or whatever you call them. Whenever I see one on eBay I always check out the motor.
Below is a quote from and earlier build showing the 66/68 Hybrid Mabuchi motor build.
Motors, I need motors!
What I'm starting out with is a motor that I like very much for the 1966 Pro type cars. It's the 1968 Mabuchi but it will be fitted to a Russkit 23 style can and epoxied and balanced to look like a period rewind. I buzzed up several of them and these two sounded very similar. One is well used and the other is like new:
Here's what the used one looks like torn down:
I asked our pal Fate what he thought the wind was and he said one wind used was 65 turns of 30 ga wire. That's a milder wind for the R&C races and that's what I want. Here's a shot of the arm with a piece of 30 ga Simco wire laid along side and above the factory wire:
Closer.........
I could only measure the wire on the factory arm with dial calipers instead of a micrometer. When I measured some Simco and La Ganke 30 ga wire I found over .001" variation between all three. Maybe there is a difference in wire coating thickness? Anyway, it LOOKS like 30 ga.
After cleaning I very lightly cleaned up the comms on the Hudy:
........and wrapped the wires leading to the comm tabs and the comm itself. I also got a fiber "oil slinger" washer ready to epoxy onto the end of the comm:
I use Devcon 2-Ton epoxy on these early arms. In the day the magazines all told us to use "Klinks" epoxy so I'm thinking Devcon is the modern hardware store "Klinks"
.....then hit it with a heat gun while I rotate it and let the epoxy sink into the windings....
........wipe any extra off with your finger and bake in your toaster oven:
One thing though...the heat makes the epoxy flow like water but it also accelerates the curing process. You have to work fast once you put the heat to it. Also, don't overheat the epoxy. If it starts smoking you're gone too far and your screwed........I did that ONCE...it's a funny story.
........and these two are ready to rock 'n roll
I broke them in at 4V for 20 minutes. They draw .4 amps and were cool as could be. I forgot to mention the arms both checked out at .8 ohms and had 5 or so degrees of CCW timing. As much as I tried to keep things the same the motor on top with the 3-balancing hole sounds faster:
Maybe that's a good thing. I'll put it up front so the front wheels will be turning fastest as has been suggested
:
Here's a shot at how clean the endbell bearing in the can is:
You can also use the armature and magnets to build a Hemi "rewound motor":
I got really lucky and scored a pair of very rare prototype RussKIT 28X (experimental) motors:
This is the standard "HEMI" can instead of the production RussKIT 28's fancy lad version with all the little slots instead of a rectangular hole.
What?
...a Tradeship HEMI end bell kit...
...the can and hardware from an American Line HEMI motor...
The armatures got the shafts straightened, the comm and comm wires tied, the comm trued and cranked a bit CCW and the whole mess epoxied and static balanced:
So for this fantasy build, these are RussKIT 28X's
So, if you can't find or reproduce a period 1966 R&C motor, give one of these a try. 
I dewound the blank and the wire on each pole was within a few inched in length of each other. 
