So I decided to start at the bottom of the pile, and build a "beater" runner out of the scruffiest chassis of the lot.

Tweaked and badly scratched nose, front shock tower missing and presumed broken, one upper link bent, steering servo gears stripped, bushings in the rear hubs, and badly worn axles and dogbones. This one was ridden hard and put away wet.
But... after raiding the parts boxes, I got it looking like this:

Full bearings, Kyosho gold shocks (don't know where the originals went, but I had these, so I used them), an old but functional Futaba S128 servo, new shock tower, and a worn Trinity Midnight motor. The motor actually turned out to be pretty much shot, so I replaced it with a simple 540J silver-can. (My yard is small anyway. Can't go much faster than that.)
I installed a Dynamite Tazer ESC and a Traxxas 2.4ghz radio, slapped on a badly-scratched-but-never-painted Viper body (I'm finding the weirdest stuff in these boxes...), and took her out for a spin.

Runs great! And my "helper" approves. The diff was slipping, so I tightened it up (yes, I checked the slipper first). Clearly, this car was run with lots of power and not much skill. But these things are built like tanks.

So hard to get a decent action shot by yourself...
So now, I'm going to paint the body, audition some other wheels and tires, and I'll have a good RC10 runner to hoon around with until we get moved and all the other toys can come out again.