So what can I do while I'm waiting for parts? All the mechanical bits, of course.

If you recall, the original motors were mounted outside-in on the bottom plate.

I mounted them that way because the wheels weren't deep enough to pass through the base, so I basically had to. Well, the new motors are HUGE by comparison, and I'm not entirely sure where they'll fit. So obviously the right answer is to guess, cut a bunch of bits off of the Dalek base, realize you need more clearance through the upper base plate too, take off the lower base plate, cut off more of the upper base plate, and then...

... no, that WAS NOT the right answer. About here, I realize there isn't enough mounting space left for the motors. They're just too big. Cue angry yelling, followed by a good long break-and-think.

Given that I don't want to cut any more of that base until I know what the hell I'm cutting, it's time to cut a new base plate. And given the size of these wheels, I can mount them in-to-out, passed through a sheet of plywood. Which might look like this?

Cut out the wheel holes, and try a quick fit:

Looks like it might just work! After marking out where the wheel posts sit, and using my router to cut a 1/4" deep notch right down the center (okay, *mostly* down the center, since I eyeballed it) - drilling pilot holes for the bolts at one size smaller than the bolts, and ... it should hold together well enough until I get some bolts and nuts to better connect them. Does it?

Yes! And OMG HOW CUTE. It's like proto-mini-Dalek-car. Which got me thinking - if this works, then I will be setting the Bob model on top of it. So if I plan it right, I should be able to mount all of the drive (and power) electronics on this motor base plate, with separable connectors to the shoulder motor board and audio board. At which point this will be a totally separable remote controlled baseplate with no Dalek. That sounds great for debugging and demonstration purposes...